Review: London's Lidos

Let’s start big picture. What’s the vibe here?
There’s something very British about clinging to the open-air life even when it’s wet and cold. London’s lidos (pronounced lee-doze) embody this attitude. Dating from the 1920s and ’30s, these outdoor cold-water pools substitute for seaside resorts on sunny days, and serve as a home for fitness nuts on wintry ones. But mostly they make for a perfect outing, complete with cafés, hot showers, and plenty of kids’ facilities. Four of the best, dotted around London’s extraordinary parks, are at Brockwell, Charlton, Parliament Hill, and London Fields. But let’s be clear: Lidos are about swimming in cold water, so they're not for the faint of heart. However, there’s nothing more exhilarating than the feeling of your circulation pumping as you pry yourself out of the water.

Any standout features or must-sees?
Brockwell Lido, in Brixton’s Brockwell Park, is a 50-meter pool from the 1930s with an award-winning café and attached fitness center. Parliament Hill Lido, on the edges of Hampstead Heath, is one of the biggest lidos in London; it's massively popular with families and triathletes-in-training. If the idea of cold water is too much but you still want to swim outside, visit London Fields lido, which is heated. After a £2 million refurbishment in 2013, Charlton Lido, in southeast London, is also heated.

Is it tough to get in?
Book online to avoid crowds, especially on sunny days; otherwise, plan to arrive early.

All said and done, what—and who—is this best for?
Unlike luxury hotel pools, London's lidos are perfect for wannabe fitness freaks who really want to get in some physical training on the cheap. If you don't like cold water, of course, take a pass.