The oldest of Reykjavik's seven public swimming pools, Sundhöllin opened in 1937 in a building by Guðjón Samúelsson (the Hallgrímskirkja architect) and has the no-nonsense modernist look of its date. An indoor 25-metre lap pool sits at ground level; outside on the roof, added much later, are hot pots, a steam room and a cold plunge with a view across the rooftops to Hallgrímskirkja.
It is the closest pool to the downtown bars, and the cheapest way to cure a hangover.