The centrepiece of Karlovy Vary's spa zone, the Hot Spring Colonnade houses the most dramatic of the town's springs: the Vřídlo, which shoots a jet of water 12 metres into the air at 73°C. The glass pavilion that encloses it was built in 1975, replacing an earlier Victorian structure, and is not particularly elegant — but it puts you close enough to the geyser to feel the heat and see the mineral deposits building up around the vent.
There are five other springs inside the colonnade, all drinkable (with a spa cup) and at varying temperatures. The Vřídlo itself is too hot to drink directly; you collect it from a tap where it has been slightly cooled. The water has a distinct sulphurous-mineral taste that takes some getting used to; the locals seem to enjoy it more than most foreign visitors.