Ooof, our thighs are burning just thinking about it. How do you fancy walking up the 36 floors (that's 828 steps) to the top of the building known as the Walkie Talkie? What if we told you someone would be waiting with a glass of champagne for you at the top? There you go.
Mencap's Step Up event is a sponsored challenge where the public will be doing just that — climbing the stairs from the ground floor, right up to the Sky Garden at the top of 20 Fenchurch Street.
The event is raising money for Mencap's campaign, to help disadvantaged people into the world of work.
Sign up as an individual or as part of a team. It's £20 per person to enter (but if you enter before 1 April and use the discount code GO16, you'll get a 20% discount). The sponsorship minimum is £200 per person or £900 for a team of five.
Step Up takes place at 20 Fenchurch Street on 17 July 2016.