Climbers, about 10 at a time, hook into a safety rigging system and follow a guide over a tensile fabric catwalk laid a few feet over the Dome’s (see box) roof, from south to north, to an observation platform at the zenith of the structure. There they pause for 15 minutes of photos of East London (the City is mostly hidden behind Canary Wharf’s towers). Beneath them, humming like a ship at sea, is a Dome conquered. The excursion isn’t for the height-averse—at your highest, you’re 52m (171 ft.) above the ground, and it’s not for big eaters or children, either (the weight cutoff is 130kg/286 lbs., and you have to be at least 10 years old), but it’s also not scary since you’re tethered, the shoes they lend you grip well, and if the weather’s bad, you get matching jumpsuits like Ooompa-Loompas. The climb, which is more like a stroll up a steep hill, takes 45 minutes, and the rest of a 90-minute experience consists of getting harnessed and psyched up.