World’s Deepest Thermal Swimming Pool is Lined with Faux Rocks

worlds deepest thermal swimming pool with realistic faux rocks
The world’s deepest thermal swimming pool, popular with divers, is lined with realistic faux rocks and crevices that plunge to 138 feet. Photos courtesy of Ideal Work

A pool in a four-star hotel in Italy gives new meaning to the phrase “deep end.” This pool, known as the Y-40 or “The Deep Joy,” in the Montegrotto Terma region of Padua, Italy, features a plunging crevasse that sinks to 138 feet (42 meters), a depth that could easily engulf a 13-story building.

Ideal Work, a leading European company in flooring, hardscaping and decorative concrete, used the company’s masterful artificial rocks to create a submerged grotto. Certified by Guinness World Records as the deepest thermal swimming pool in the world, the pool has become a popular attraction for scuba divers and freedivers, athletic divers who hold their breath and don’t use air tanks.

blue print of worlds deepest pool

Established in 1996, Ideal Work in Treviso, Italy, has created some of Europe’s most beautiful classic, Old-World style and modern stamped and stained concrete, including cementitious toppings and overlays. Luca Seminati, Ideal Work’s managing director, says the company helped create the marine setting, which was completed in June 2014, constructing four grottos at the bottom of the pool with very natural and realistic effects.

“The grottos were created with Ideal Tix plaster,” says Seminati. “It was developed for uses requiring substantial thicknesses, up to 6 or 7 centimeters [almost 3 inches] and high durability.” The plaster works well in settings that have direct contact with water such as swimming pools, spas and water parks.

The Deep Joy, part of the amenities of the Hotel Terme Millepini, a 100-room luxury hotel just outside of Venice, is filled with a mineral-rich water that emerges from local springs at about 190 degrees Fahrenheit (87 degrees Celsius) and is brought down to a constant temperature of about 91 degrees F (33 to 34 degrees C). The water’s temperature allows divers to take the plunge without the wet suits they’d need in open seas.

worlds deepest pool

Created by architect Emanuele Boaretto, the pool is designed very distinctively, says Seminati. It features underwater caves and a suspended, transparent tunnel beneath the surface that guests can walk through. Viewing platforms are installed at various depths, ranging from 4 feet (1.3 meters) to 39 feet (12 meters). Below these platforms, the walls of the pool narrow into a funnel which plunges straight down to the full depth of the pool.

“The large windows at the sides of the basin 5 meters [16 feet] down create a space where the internal and external transparency intermingles. This detail enables spectators to cross the swimming pool horizontally, with all-around visibility above and below.”

The materials used to create the grottos at the pool’s bottom needed to be capable of being submerged without undergoing noticeable changes over time. Ideal Work was chosen to construct the grottos because of its outstanding track record pertaining to water parks, spas and theme parks it has worked on. Once the Ideal Tix plaster was applied, a special rubber mold was used to create texture.

worlds deepest pool

“The artificial rocks obtained through this process give the swimming pool great natural and realistic scenic impact, blending perfectly with the surroundings,” says Seminati. “The grottos are coated with special protective treatments that make them resistant to environmental conditions. They require only limited maintenance and also retain a perfect appearance over time.”

The Ideal Work system allows artificial rocks, such as those in the Deep Joy, to be created quickly and easily, because the company only works with trained installers. “Professional installation enables and guarantees the creation of unique work such as this unique pool, which can be found in only one place in the world,” says Seminati.

Project at a Glance

Client: Hotel Terme Millepini, Montegrotto Terme, Padua, Italy

Contractor: Ideal Work, Treviso, Italy |

Scope of project: Creating realistic-looking artificial rocks for caves and grottos in the world’s deepest swimming and diving pool.

Most challenging aspect: Products need to look good and stay intact while being constantly submerged.

Products used: Ideal Work’s Ideal Tix plaster

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