The Lee Valley White Water Centre — built for the canoe slalom events of the London 2012 Olympics — is one of the very few Olympic venues that has thrived as a public attraction afterwards. There are two pumped courses, a 300-metre Olympic-standard channel for serious kayakers and a shorter 160-metre course for first-timers, both running constantly with 13 cubic metres of water per second.
You don't need to be a paddler to use it. Six-person inflatable rafts run regular trips down the easier course with a guide steering — about 90 minutes of getting soaked and yelling, often with stag and hen parties on board. Hot-dog kayaking and "hydrospeeding" (riding the rapids on what is essentially a giant float) are also bookable. The centre sits in a pleasant patch of the Lee Valley park, with a café and outdoor terrace overlooking the start gate.