No, it's not Willy Wonka's Chocolate Factory! Althought you'd be forgiven for thinking that the madcap boating lake on London's Selfridge's rooftop was part of it.
The Bompass and Barr boys (Sam Bompass and Harry Parr) came up with their 'most ambitious project ever' - The Truvia® Voyage of Discovery installation - after UK importers of Truvia®, a calorie-free sweetener, from a stevia plant, which is apparently 200 times sweeter than sugar, sponsored them to.
Open to the public from 21-24 July 2011, there's a (dyed) emerald green boating lake (which required B&P to get hold of a pleasure boat license from Westminster Council), thousands of stevia plants, 12 rowing boats, a gushing waterfall and a Selfridges life guard.
Drinks-wise, cocktails will be by the Experimental Cocktail Club whose bar in Chinatown has been drawing rave reviews since it opened. Teas will be from the Rare Tea Company and Caravan is responsible for the coffee.
Sam and Harry said: 'The installation takes Selfridges' roof back to its proper place as a pleasure spot - it once hosted gardens, cafes, golf courses and an all girl gun club.'
They managed to reinforce the roof at Selfridges with miles of steel to allow it to be flooded to create it. The inspiration came from a gondola party that was thrown at The Savoy in 1905 (so not Willy Wonka, then), when the courtyard was flooded, and elephants and opera singers provided the entertainment.
Well, we've heard of rootop bars, but rooftop lakes is a new one on us...
For tickets, see the Bompass & Parr website jellymongers.co.uk