Y-40 The Deep Joy

What to expect

Y-40 The Deep Joy is not a hot spring you soak in. It is a training pool for scuba divers and freedivers, built next to the Hotel Terme Millepini in Montegrotto Terme and filled with the same hot mineral water that feeds the town’s spa hotels. We list it because so many visitors to the Euganean spa towns come to see it, and because it is the strangest use of thermal water in Italy.

The design, by the architect Emanuele Boaretto, took a year to build, from May 2, 2013 to May 1, 2014. It opened on June 5, 2014, with the freediving legends Enzo Maiorca and Umberto Pelizzari there for the launch, and entered Guinness World Records as the deepest pool in the world. Other, deeper pools have been built since, and Y-40 now describes itself as the deepest pool with thermal water.

The numbers:

• Depth: 42.15 m (138 ft) at the bottom of the central shaft.
• Volume: about 4.3 million litres (1.1 million US gallons) of thermal water.
• Water: 189°F87°C at source, 90-93°F32-34°C in the pool.
• Features: platforms at several depths, three freediving lines in the deep shaft, a glass tunnel at 5 m, a bar-bistro looking into the water, and artificial caves for cave-diving practice.

What non-divers can do

This is the question most visitors have, and the answer is clear on Y-40’s own pages.

• Watch for free. Anyone can walk in and look. You can watch from the Bar Bistrot, set 5 m (16 ft) down with underwater windows, and walk through the transparent tunnel suspended 5 m (16 ft) down, with divers and freedivers moving around and below you.
• Take a guided tour. A paid guided visit explains the architecture and how the pool works. Groups, schools and companies can book tours at a flat price.
• No swimming tickets. Y-40 does not sell entry for ordinary swimming. If you came for a warm soak, the operator points you to the SPA Day at the Hotel Terme Millepini next door, open to outside guests every day from 9 a.m. to 7 p.m., with booking advised. Millepini has three thermal pools covering more than 1,000 square metres.
• Try a first dive. If you are curious enough to get in, you do not need a certificate.

Diving and first experiences

First experiences are for people with no diving certificate. Y-40 instructors take you gradually from shallow water down to a maximum of 12 m (39 ft), and you go only as deep as you are comfortable with. There are four types: freediving (holding your breath), scuba (breathing from a tank), “mermaid and merman” sessions with a monofin, and junior sessions for ages 8 to 14. Adult sessions are for ages 15 and up, and anyone under 18 needs a signed responsibility form. Group sessions run on set days; private ones can be booked for a date you choose.

For scuba you get fins, BCD, tank, regulator and mask. Bring a swimsuit, a bathrobe and flip-flops. In October 2026 the gift cards for a first scuba experience were priced at €99 in a group and €139 with a private instructor, and the same values could be used for any instructor-led activity. Check current prices in the online shop.

Certified divers book timed sessions: 85 minutes for freediving and 45 minutes for scuba. You must bring your certificate and dive with a certified buddy or an instructor. Arrive an hour early. Night scuba runs from October to May. Y-40 also hosts courses up to instructor level, workshops with freediving champions, and pregnancy and baby water classes run by the Amani association in the thermal water.

Getting there

Y-40 is at Via Catajo 42, Montegrotto Terme, south-west of Padua, on the same site as the Hotel Terme Millepini.

• By car: From the A13, leave at Terme Euganee and drive about 5 km (3 miles). From the A4, leave at Padova Ovest and drive about 18 km (11 miles). Free parking is along Via Catajo, about 50 m past the entrance on the right.
• By train: The nearest station is Terme Euganee Abano-Montegrotto, 1.7 km (1.1 miles) away. High-speed trains stop at Padua, where you change to a regional train.
• By bus: A public bus between Padua station and Montegrotto Terme (Turri) stops at Y-40, via central Padua and Abano Terme.
• By bike: Flat cycle paths link Y-40 with Padua along the Battaglia canal and with the E2 ring around the Euganean Hills, about 60 km (37 miles).
• From airports: Venice Marco Polo is 64 km (40 miles) away, Treviso 86 km (53 miles), Bologna 106 km (66 miles) and Verona 107 km (66 miles).

When to go

Y-40 is indoors, so weather does not matter. Opening times and dive slots vary, and the timetable on the website is the one to trust; the operator suggests simulating a booking to see real availability. If you only want to watch, choose a time when sessions are running so there is something to see.

Rules and etiquette

• No solo diving: always with a certified buddy or a Y-40 instructor.
• Certificate compulsory for everyone except beginners with an instructor.
• You sign a statement that you are fit, can swim unaided and are comfortable in deep water.
• Lanyards are compulsory on the freediving lines, and the three lines rotate.
• No recreational swimming.

Where to stay nearby

The Hotel Terme Millepini shares the site and has its own thermal pools and spa. Montegrotto and Abano Terme have many more thermal hotels; Terme Preistoriche is about 1.3 km (0.8 miles) north. Padua has the widest choice of cheaper rooms.

Safety notes

• Diving and freediving carry real risks: ear and sinus squeeze, blackout and loss of motor control in freediving, and decompression problems in scuba. Y-40 lists these on its site. Tell an instructor at once if something feels wrong.
• Do not fly within the usual no-fly period after scuba diving, even in a pool. Ask your instructor.
• Warm 90-93°F32-34°C water feels easy, but it is still deep water. Do not go below the depth your training allows.

Nearby stops worth adding

The Euganean Hills rise right behind Montegrotto, with Castello del Catajo a short ride south and Arquà Petrarca, Monselice and Este further on. For a soak in the same water without the depth, book a day at Hotel Terme Millepini or at Terme Preistoriche.