(CNN) — It's one of the most beautiful cities in Europe, but Budapest can also make a claim to be one of the most relaxing, thanks to a secret buried beneath its beautiful architecture.
Bubbling up through the city's limestone foundations are 118 natural thermal springs that deliver 70 million liters of therapeutic waters each day.
No wonder they call it the "City of Spas."
The Turkish baths of Budapest are exquisite, an everlasting memory of Ottoman rule during the 16th and 17th centuries, renowned the world over for their relaxing and medicinal purposes.
Not only are there a whole host of thermal spas dotted around, but outdoor swimming pools play a huge part in making summer (and winter) even more enjoyable in the city.
Here are 10 top spa and swimming destinations that are worth checking out when you travel to Budapest:
Nestled beneath Gellért Hill on the banks of the Danube river, Rudas Baths is one of the more favored thermal spas in Budapest.
Dating back to 1550, it has the look and feel of what one would expect of a traditional Turkish bath house during Ottoman rule.
A large octagonal plunge pool takes center stage, accompanied by five smaller thermal pools, a sauna, steam room and massage rooms.
The spa also holds modern annex houses, a larger swimming pool and a rooftop hot tub, which is bustling in both the summer and winter months.
Admission fee: $18.60 during the week and $23 at weekends. Steam bath open daily from 6 a.m. to 8 p.m.
Rudas Baths, Budapest, Döbrentei tér 9, 1013 Hungary; +36 1 356 1010
Olympic Champion swimmer Katinka Hosszu shows CNN Travel the watery highlights of Budapest.
Built in 1913, the Széchenyi Baths is a Budapest must-see and remains hugely popular with travelers.
Situated in the heart of the City Park, the bath house is one of the largest in Europe and the only thermal spa on the Pest side of the city.
Its three huge outdoor pools are open year round, providing a great place to sunbathe during the summer months.
Winter is also an experience here -- jumping between one of the 10 indoor pools to the outside bathing area certainly wakes you up.
Its saunas, steam chamber and massage rooms are plentiful inside, with a number of treatments available upon request.
Admission fee: Around $21 on week days and $22 at weekends. Open daily from 6 a.m. to 10 p.m.
Széchenyi Baths, Budapest, Állatkerti krt. 9-11, 1146 Hungary; +36 1 363 3210
Gellért Baths -- one of Budapest's most beautiful bathhouses.
Courtesy Gellért Baths
The Gellért Baths are based inside the grand Gellért Hotel, which opened in 1918 and is a prime example of the Art Nouveau style constructed in Hungary throughout that period.
Perched at the foot of Gellért Hill, the building is famous throughout Hungary and has featured in many local and international films.
The bathhouse complex was expanded to include an outdoor pool with a wave-generating machine in 1927.
It also boasts a steam room, sauna, sun terrace, thermal baths and massage rooms complete the baths that provide an inviting pool area whatever the weather.
Admission fee: $22 on weekdays and $23 at weekends.
Gellert Baths, Budapest, Kelenhegyi út 4, 1118 Hungary; +36 1 466 6166. Open daily from 6 a.m. to 8 p.m
Király Baths dates back to 1565.
Courtesy Király Baths
One of the oldest spas in the city, Király Baths is housed in one of the few buildings in Budapest that was erected during the time of the Ottoman rule.
Built in 1565, its magnificent cupola-topped pool is its main draw. The bathhouse also includes a thermal pool, massage rooms, a sauna and steam room.
A recent addition to the spa came in the guise of a Finnish sauna complete with a cold plunge pool, which has been a huge hit with locals.
Admission fee: $10. Open daily from 9 a.m. to 9 p.m.
Király Baths, Budapest, Fő u. 84, 1027 Hungary; +36 1 202 3688
The Lukács Baths feature both indoor and outdoor pools.
Courtesy Lukács Baths
Situated on the Buda side of the city, the thermal springs at Lukács Baths have been in use since the 12th century.
The historic building became a healing spa and treatment center at the end of the 19th century, and its inner courtyard is emblazoned with marble tablet engravings of gratitude from those who were treated here.
Lukács Baths was most recently renovated in 2012 and is now made up of four warm thermal baths, a cold plunge pool and a number of massage and treatment rooms.
Admission fee: About $14 on week days and $15 at weekends. Open daily from 6 a.m. to 10 p.m.
Lukács Baths, Budapest, Frankel Leó út 25-29, 1023 Hungary; +36 1 326 1695
The Royal Spa at the Corinthia Hotel Budapest
The Royal Spa at the Corinthia Hotel Budapest's galleried 15-meter swimming pool.
First opened in 1886, the Royal Spa at the Corinthia Hotel is one of the most luxurious spa destinations in Budapest.
Its pièce de résistance is a galleried 15-meter swimming pool, which is housed in an ornate architectural masterpiece.
Relaxation rooms, saunas, a steam bath and Jacuzzis are also available to visitors as well as an array of ESPA treatments if you care for a relaxing facial or body massage.
Admission fee: $33. Open daily from 6.30 a.m. to 10 p.m.
The Spa at Four Seasons Hotel Gresham Palace Budapest
This spa offers a range of treatments such as a Hungarian moor mud wrap.
Four Seasons Hotels and Resorts
Based in the exclusive Gresham Palace, Four Seasons Budapest is considered among the finest five-star hotels in the city.
Its in-house spa is also a delight, positioned up high overlooking the city.
Complete with a relaxation pool, sauna, separate steam rooms for men and women and a whirlpool, one can easily while away the hours relaxing the day away here.
There are also several private rooms offering sensual massages along with Vichy shower treatment rooms.
Admission fee: Around $37.50. Open daily from 6 a.m. to 10 p.m.
Veli Bej (or Császár Baths)
Veli Bej -- one of the most stunning
Ottoman-era baths in the city.
Courtesy Veli Bej
Originally commissioned by Ottoman statesman Szokullu Musztafa, Veli Bej (also known as Császár Baths) was considered the most beautiful baths of its time when it was built in the 16th century.
Beautifully renovated in 2017, its focal point is a large octagonal hot water pool, which is surrounded by four smaller pools.
The ornate building also boasts a modern swimming pool, steam baths, sauna, Jacuzzi and a special bathtub for hydrotherapy.
Admission fee: $10. Open daily from 6.00 a.m. to 9 p.m.
Veli Bej, Budapest, Árpád fejedelem útja 7, 1023 Hungary; +36 1 438 8587
Danubius Health Spa Resort Margitsziget, Margaret Island
Danubius Health Spa Resort Margitsziget uses three water sourced from three natural springs.
Danubius Health Spa Resort Margitsziget
Situated in the center of the city, Margaret Island is known as the "Spa island of Budapest."
Visitors can experience the island's thermal waters in various locations, but the Danubius Health Spa Resort Margitsziget is one of the stand outs.
Water sourced from three natural springs are used in the hotel's thermal bath as well as its indoor and outdoor swimming pools, hydrotherapy bath, sauna, steam and aroma baths.
Admission fee: $20.60 on week days and $24 at weekends. Open daily from 6:30 a.m. to 9:30 p.m.
Palatinus Baths, Margaret Island
Palatinus has been around since 1919 and is open all year round.
Palatinus Baths was the first location in Hungary to allow visitors to bathe outside.
It's now a top spot for both locals and tourists, who flock here during the summer time to sunbathe and take advantage of the 11 different pools.
Not only does it hold thermal baths and mineral waters taken from the natural springs on the island, Palatinus also has giant water slides and a wave pool on site.
A new wellness center, which boasts a Finnish sauna, geothermal sauna and steam chamber, was added in 2017.
The cold and hot water plunge pools also help to make this one of the top places to visit in the city during the summer months.
Admission fee: $11.50. Open daily from 8 a.m. to 8 p.m.