A few kilometers from Naples, under the sea of the Campi Flegrei, lies one of the most extraordinary Roman cities in the Mediterranean: ancient Baiae, the "Las Vegas of the Roman Empire," the spa-and-vice town where Roman patricians spent their holidays, where Caesar and Augustus kept villas, where Nero had his mother killed. Today you can see it from the floor of the Gulf of Pozzuoli by snorkeling and diving, one of the most singular experiences Italy can offer.
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The story of Baiae: the most decadent city of the Roman Empire
Baiae (the ancient Roman city, today Baia, a frazione (outlying hamlet) of the Comune of Bacoli, NA) was the most famous seaside destination of the Roman Empire, a town of baths, villas, brothels, and unbridled luxury that Roman moralists (from Seneca to Horace) described with disgust and that patricians frequented with enthusiasm. Julius Caesar had a villa here. Augustus died on his way back from Baiae (in AD 14, at Nola). Here Nero had the trick boat built with which he tried to kill his mother Agrippina (the killing was finished on the shore with daggers). Horace wrote "nulla est in orbe sinus Baiis praelucet amoenis," no bay in the world outshines lovely Baiae. The city was abandoned in the 7th century AD because of Saracen raids and volcanic bradyseism (the geological phenomenon of the Campi Flegrei that lowers and raises the ground). Bradyseism submerged the entire area of the ancient city between the 9th and 13th centuries, today the Roman structures lie at 3-12 m of depth below the surface.
The Underwater Park of Baia: what you can see
The Underwater Park of Baia (established in 2002, Italy's first underwater park) protects about 177 hectares of seabed where the structures of ancient Baiae are visible: mosaic floors of Roman villas (the mosaic of the "Villa dei Pisoni" is the most visible, at 3 m depth, visible even while snorkeling in the clear water of July-September). Columns and capitals of the Roman port. Statues in situ (copies, the originals are in the Archaeological Museum of the Campi Flegrei in Bacoli). Remains of baths, nymphaea, and cisterns. The main sites: the Villa with the entrance (visible while snorkeling at 0-4 m), the Portus area (the Roman port, 5-8 m), the Nymphaeum area (8-12 m, for certified divers only).
How to visit the Underwater Park of Baia in 2026
There are three ways to visit the Underwater Park of Baia:
- Glass-bottom boat: the most accessible option, boats with underwater viewing run by authorized operators (€15-25/person, about 1 hour, you don't get in the water). Operators: Centro Sub Campi Flegrei (www.centrosubcampiflegrei.it), Baia Dive Resort. Suitable for children, older travelers, and non-swimmers.
- Guided snorkeling: for those who can swim, you get in the water with mask and fins, led by an instructor. The snorkeling sites (0-4 m deep) are visible in good-visibility conditions in July-September. Cost: €25-40/person (2 hours). Available only in summer (July-October for the water temperatures).
- Scuba diving: for certified divers (at least Open Water). The deeper sites (5-12 m) with the most intact structures. Cost: €50-80/person (two dives, guide included). Local operators rent equipment (€15-25 surcharge). Booking required.
Practical logistics: how to reach Baia from the Campi Flegrei and from Naples
Baia is reached from Naples: take the Cumana from the Montesanto station in Naples to Fusaro or Torregaveta (Cumana line, 40 min, €1.30). Then a taxi or local bus to the port of Baia (Bacoli), or a local bus from the Fusaro station. By car: the Naples-Rome motorway, Pozzuoli exit, plus the Tangenziale expressway, Bacoli exit. Parking is available at the port of Baia. The Archaeological Museum of the Campi Flegrei (Castello di Baia, Bacoli, home to the originals of the submerged statues, including the Caesar of Baia, the most realistic portrait of the emperor ever found) is worth visiting before or after the underwater park: €8 admission, Tuesday-Sunday 9:00-18:00.
Questions and answers about Baia Sommersa
Baia Sommersa Pozzuoli: can you really see anything without scuba diving?
Yes. In the summer months (July-September), with clear water (8-15 m visibility) and the glass-bottom boat, you clearly see the mosaic floor of the Villa dei Pisoni at 3-4 m depth, the Roman columns and capitals, some wall structures. Snorkeling lets you see even more, the mosaics look razor-sharp free-diving at 2-3 m. The water visibility in the Gulf of Pozzuoli varies a lot by season: in summer (July-September) it's at its best. In winter and spring the rains bring turbidity. Always book in July-August, the spots sell out.
Baia underwater park: is it suitable for children?
The glass-bottom boat is suitable for children of any age, you don't get in the water, and kids often see better than adults through the glass thanks to their lower height. Snorkeling is suitable for children aged 8 and up who can swim with mask and fins. Scuba diving requires a minimum Open Water certification (trainable from age 10). Children who visit the Underwater Park of Baia often say it's "the most beautiful thing they've seen in Italy," the spell of the submerged Roman city is immediate at every age.
What to see in Pozzuoli and the Campi Flegrei beyond Baia Sommersa?
The Campi Flegrei (the volcanic district west of Naples) are one of the most extraordinary and least visited places in Campania. Worth seeing: the Solfatara of Pozzuoli (an active volcanic crater with sulfur and fumaroles, spectacular; €8 admission). The Flavian Amphitheater of Pozzuoli (the third largest in the world after the Colosseum and Capua). Bradyseism visible in the remains of the Macellum of Pozzuoli (the ancient Roman market where the columns show the holes bored by marine mollusks during the periods when the ground had dropped below sea level). The Archaeological Museum of the Campi Flegrei in Bacoli (Angevin castle) is the logical final stop after the underwater park.
Baia Sommersa: when is the best time to visit?
July-September for maximum water visibility (15+ m), water temperatures of 24-26°C, and comfortable snorkeling without a wetsuit. May-June and October as a second choice: visibility still good, cooler water (18-22°C). November-April: the glass-bottom boat can go out in calm seas, but snorkeling isn't advised because of the water temperatures (12-16°C). Always book at least 1 week ahead in summer, the diving and snorkeling groups fill up fast.
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There's an Italy that doesn't show up in the travel guides, not because it's hidden, but because the guides are written for mass tourism and mass tourism wants the same 20 things in every country. The real Italy, the one of small trattorias with no translated menu, of villages where the mayor is also the bartender, of patron-saint festivals that run a full week with the town band playing at 11:00 p.m., is right there in plain sight, but it asks you to slow down enough to notice it. The travelers who come home in love with Italy aren't the ones who saw the most places, they're the ones who stopped long enough to catch the smell of ragù drifting out of a third-floor window, to learn the bartender's name and get him to point them to a "real" place to eat.
Cross-cutting practical tips for any trip to Italy
How the "coperto (fixed per-person cover charge)" (cover charge) works in Italian restaurants, and when it's legal
The "coperto" (cover charge) in Italian restaurants, the line that shows up on the bill as "coperto" or "pane e coperto" (bread and cover), is a regionally regulated practice in Italy. In some regions (Lazio, Tuscany, Emilia-Romagna) the coperto is legal if shown on the menu posted at the entrance. In others (Veneto, Lombardy) it has been abolished. The coperto ranges from €1 to €3/person. Italian law requires the price of the coperto to be visible on the menu before you sit down, if it's not on the menu, you can legally contest it. Don't confuse it with the "servizio" (service charge, 10-15% at some upscale restaurants), which is owed only if stated on the menu. Practical tip: always read the menu posted outside before sitting down, it lists prices, coperto, and VAT.
The Italian ZTL (Zona a Traffico Limitato, limited-traffic zone): how to avoid a fine when driving a rental car
Italian ZTLs are old-town areas open only to authorized vehicles (residents, taxis, buses) at certain hours, the cameras read plates automatically and the fines arrive at the home of the vehicle's owner, which in the case of a rental car is the rental company, which passes the fine on to the customer adding an administrative fee of €25-35. ZTLs aren't always clearly marked for tourists. How to avoid the fine: ask your hotel whether your lodging is in a ZTL (many hotels can register your plate for temporary access). Use Google Maps with the "avoid ZTL" setting (available on updated maps). In the main historic cities (Rome, Florence, Siena, Bologna) park outside the center and use public transport or a bike. Florence's ZTLs are particularly strict, the historic center of Florence is almost entirely ZTL 24/7.
Your phone in Italy: which SIM or eSIM to buy as a tourist in 2026?
The main options: a physical SIM (TIM, Vodafone, Iliad, WindTre, available in tobacconists/newsstands and operator stores in every city. ID required to buy; €10-20 for a SIM with a 10-20 GB data package valid 30 days). A virtual eSIM (Airalo, Holafly, BNESIM, bought online before you leave, activated by QR code. Price similar to the physical SIM. For eSIM-compatible smartphones, meaning iPhone 12+ and many 2021+ Androids). Italian networks have good 4G coverage in all urban areas and on the motorways. Reduced coverage in some rural and mountain areas. For EU citizens: EU roaming lets you use your own operator's data plan in Italy at the domestic rate, check with your operator if you're in the EU.
Italian pharmacies: how they work for foreign tourists
Italian pharmacies (recognizable by the green cross) are among the most accessible and competent in Europe, Italian pharmacists hold a 5-year university degree and can give basic medical advice without a prescription (for common ailments). Pharmacies are generally open 9:00 to 13:00 and 15:30 to 19:30, Monday to Saturday. For nighttime and holiday emergencies, the "farmacia di turno" (on-duty pharmacy) service is mandatory, you find the list of pharmacies open around the clock on the panel posted on every closed pharmacy, or by searching "farmacia di turno + city" on Google Maps. Common European medicines (painkillers, antihistamines, antacids) are available without a prescription. Prescription drugs from your country may require a new Italian prescription, always carry the original medical documentation for chronic medications.
Italian curiosities that travelers find unexpected
- Italy is the country with the most UNESCO sites in the world (58 in 2025, ahead of China and France)
- The pizza margherita was "invented" (or at least named) in 1889 by the Neapolitan pizzaiolo Raffaele Esposito in honor of Queen Margherita of Savoy, the colors (red tomato, white mozzarella, green basil) represented the Italian tricolor
- Parmigiano Reggiano is treated as a "guaranteed" safe-haven asset by banks, some Emilian banks accept wheels of aged Parmigiano Reggiano as collateral for farm loans
- The word "paparazzo" comes from a character in Fellini's film La Dolce Vita (1960), the photographer Paparazzo. The plural paparazzi went international thanks to the film
- The University of Bologna (founded in 1088) is the oldest university still operating in the world, it predates Oxford by about a century
- The Venetian dialect was the lingua franca of trade in the eastern Mediterranean in the 15th century, even today on some islands of the Croatian Adriatic you find traces of Venetian in the local dialect
- The Sicilian arancino comes in two shapes: rounded (like an orange) in western Sicily (Palermo), pointed like a cone (like a volcano, probably a nod to Etna) in eastern Sicily (Catania). The dispute over the name is serious: in Catania it's "arancino" (masculine), in Palermo it's "arancina" (feminine)
- Italian motorway signage is blue (not green as in most of Europe), an Italian quirk born in 1955 and never updated to the European convention
Accessible Italy: services for travelers with special needs
Accessibility in Italy has improved significantly over the last 10 years, but it's still uneven. The most visited state museums (Colosseum, Vatican Museums, Uffizi) have wheelchair-accessible routes and services for visitors with low vision and hearing impairments (book ahead specifying your needs). Italy's most accessible cities: Bologna (covered porticoes, even paving), Florence (many flat areas in the center), Rome (alternatives to stairs at most monuments). The hardest cities for wheelchair users: Venice (bridges everywhere, water, no traditional land transport), Positano (500+ steps between the sea and the upper road), the perched medieval villages. The go-to online resource: Turismo Accessibile (www.turismoraccessibile.it) has maps and guides specific to each Italian destination.
Campi Flegrei and bradyseism: the volcano under Pozzuoli
Baia Sommersa isn't only an archaeological site, it's also one of the places where the geological phenomenon of bradyseism is visible in its most spectacular form. Bradyseism (from the Greek bradys "slow" and seismos "movement") is the slow rising and sinking of the ground caused by the activity of the Campi Flegrei volcanic system (the largest volcanic caldera in Europe, about 13 km across, taking in Pozzuoli, Bacoli, Baia, Miseno, and part of the city of Naples). Bradyseism lowered the ground of Pozzuoli by 10-13 m between the 9th and 13th centuries, flooding all of Baiae. The process reversed in the 20th century: between 1982 and 1984 the ground rose 1.8 m in 2 years, forcing the evacuation of 40,000 Pozzuoli residents and causing significant structural damage. Today the Campi Flegrei are monitored 24/7 by the Vesuvius Observatory (INGV), the system has been in a phase of positive bradyseism (uplift) since the 2000s. The Macellum of Pozzuoli (the ancient Roman market visible at the surface) shows bradyseism perfectly: the mid-height marble columns show the holes bored by marine mollusks (the lithodomi, rock-boring date mussels) during the periods when the columns were submerged by the sea under negative bradyseism.
Baia Sommersa: are there safety risks diving in the Gulf of Pozzuoli?
Diving in the Underwater Park of Baia is safe when done with authorized operators and inside the marked zones of the park. The specific risks to consider: the seabed's geothermal activity (underwater fumaroles releasing hot gases in some areas of the gulf, operators know the safe areas and keep them off the routes). Currents (generally weak in the gulf, but variable with the weather). Reduced visibility after rain (the gulf gets murky with runoff from the surrounding hills). All authorized operators of the Underwater Park of Baia carry insurance, trained guides, and safety equipment, don't improvise solo dives without a guide even if you're advanced-certified.
Baia underwater: is it worth it compared to other snorkeling experiences in Italy?
Baia Sommersa is unique in Italy and in the Mediterranean, there's no other Roman city you can see while snorkeling anywhere else. Comparing it to Italy's marine reserves (Portofino, Ustica, Tremiti) isn't fair: those offer exceptional marine life. Baia offers underwater archaeology in a natural setting. If you've already snorkeled in Italy's marine reserves and want something completely different, Baia is the answer. If it's your first snorkeling experience in Italy: pick a marine reserve with abundant fauna first (more spectacular for those who don't know the Roman historical context), then come back to Baia with more cultural context.
