Stairs are radically underappreciated. Great for leg strength and general fitness. Walking up stairs (say in at a train station) is almost always faster than using an escalator, even if you're not particularly fit. Walking up an escalator is even faster, of course, but there's a always a couple of muppets getting in the way. Stairwells, unlike lifts, haven't been implicated in coronavirus transmissions either, so that's an extra bonus. And if you're a gym person, the stairmaster seems like the least popular piece of equipment, so it's almost always available for use.