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:

Rudas Baths

Nestled beneath Gell-rt 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, D-brentei t-r 9, 1013 Hungary; +36 1 356 1010

Sz-chenyi Baths

Built in 1913, the Sz-chenyi 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.

Sz-chenyi Baths, Budapest, -llatkerti krt. 9-11, 1146 Hungary; +36 1 363 3210

Gell-rt Baths

The Gell-rt Baths are based inside the grand Gell-rt 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 Gell-rt 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 -t 4, 1118 Hungary; +36 1 466 6166. Open daily from 6 a.m. to 8 p.m

Kir-ly Baths

One of the oldest spas in the city, Kir-ly 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.

Kir-ly Baths, Budapest, F- u. 84, 1027 Hungary; +36 1 202 3688

Luk-cs Baths

Situated on the Buda side of the city, the thermal springs at Luk-cs 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.

Luk-cs 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.

Luk-cs Baths, Budapest, Frankel Le- -t 25-29, 1023 Hungary; +36 1 326 1695

The Royal Spa at the Corinthia Hotel Budapest

First opened in 1886, the Royal Spa at the Corinthia Hotel is one of the most luxurious spa destinations in Budapest.

Its pi-ce de r-sistance 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 Royal Spa at the Corinthia Hotel, Budapest, Erzs-bet krt. 43-49, 1073 Hungary; +36 1 479 4000

The Spa at Four Seasons Hotel Gresham Palace Budapest

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.

The Spa at Four Seasons Hotel Gresham Palace Budapest, Sz-chenyi Istv-n t-r 5-6, 1051 Budapest; +36 1 268 6000

Veli Bej (or Cs-sz-r Baths)

Originally commissioned by Ottoman statesman Szokullu Musztafa, Veli Bej (also known as Cs-sz-r 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, -rp-d fejedelem -tja 7, 1023 Hungary; +36 1 438 8587

Danubius Health Spa Resort Margitsziget, Margaret Island

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.

Danubius Health Spa Resort Margitsziget, Margaret Island, Budapest-Margitsziget, 1007 Budapest, Hungary; +36 1 889 4700

Palatinus Baths, Margaret Island

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.

Palatinus Baths, H-1007 Budapest, Margaret Island; +36 1 340 4500