Budapest the Spa city
When the Celts who lived on the territory of the city in ancient times named their settlement AK-INK-meaning „Abundant Water” Good Water” they did not mean the water of the Danube. Abundant and good water meant for them and later for the Romans the water of the springs that had their sources at the foot of the mountains.
The springs are connected to the structural line along the eastern edge of the Buda Mountains to the so called thermal line.
(the ancient Romans and later the Turks built their bath along this volcanic fault line)

It is a unique natural characteristic feature that 136 thermal springs have their sources in our capital and they give daily 70 millions litre of water.
The springs along the Danube banks in Buda start out with 23-24 ºC warm springs in the North and they provide water for the Pünkösd Bath and the Roman Bath.
A group of springs with 24-58 ºC curative thermal water has its source southwards on the territory of Lukács Császár Bath and at the foot of Gellért Hill(Rudas and Gellért Bath)
The thermal wells found on Margaret Island provide water for its thermal hotles and the Óbuda district.
The temperature of the water springing from the wells in the south part of the capital is higher because these waters come from deeper sources.The Széchenyi Bath and Spa in the City Park on Pest side is provided with 73-76 ºC thermal water.
Intersting fact that in the Budapest Zoo (City Park Pest side) the pool of the hippopotamuses is supplied with the thermal water source of Széchenyi Bath because the chemical composition of the water is very similar to the composition of the water in the River Nile.
(Source KIT : Welcome to Budapest)