Yoga's often said to take you to new heights, but this is taking things very literally. While London's glitziest office block might not be the most intuitive place to seek inner calm, your view of the clouds will no doubt override any misgivings about Mammon. This weekly yoga class takes place at 800ft, making it the world's highest, and is an hour long, with 15 minutes either side for taking in the incredible view. In good weather the class will take place on the open-air viewing platform, as long as the wind isn't strong enough to knock over any downward-facing dogs. Mats are provided. Book in advance.