Nearest Station: Herne Hill
London has a number of outdoor pools, but Brockwell Lido is arguably the prettiest, with its refurbished 1930s buildings nested up against Brockwell Park. On warm-weather days, it fills up (as do other pools in places like Tooting Bec, Finchley, and London Fields) and the atmosphere is full of fun. On quieter, colder days, only the brave take to the pool. Others visit the incredible onsite cafe instead, which is worth a visit even if you're not planning a swim later.