We moved to London a month ago, and it didn't occur to us that our apartment (newish building) might not have air conditioning until we signed the lease. It hasn't been much of a problem, but the coming week of hot weather coupled with our toddler and a set of grandparents (mid-70s, active but not super mobile) coming to visit has me searching for ways for us to get out of the house and cool off. We're already planning on hitting up a couple museums, and I know a walk through St. James's Park is in our future, but any suggestions, especially for day-trips out of the city, would be greatly appreciated.