A listed Art Deco swimming complex of 1924, the Piscine de la Butte-aux-Cailles is built in warm red brick over a vaulted hall and fed by water drawn from a deep artesian well beneath the quarter — naturally warm and a little mineral. There is the handsome historic indoor pool under its arched roof, plus two outdoor pools that open in summer.
It is a working municipal baths rather than a museum, so it keeps pool hours and gets busy, but it is one of the loveliest places to swim in Paris and a genuine piece of neighbourhood heritage. Worth timing a visit around if you fancy a dip; otherwise admire the brick façade from the street.