West Ham Bus Garage is London's newest, biggest and greenest bus garage, so it's no wonder that London Transport Museum and Stagecoach are keen to show it off.
Tomorrow, for one day only, the public can enter the building, usually off limits to all but a select few. Two separate events will run, one at 9.45am and the other at 1pm.
Architect Malcolm McGregor, of Pringle Richards Sharratt, will be sharing the design secrets while the London Transport Museum's Oliver Green will be talking about the creation of the garage, built to replace two depots in Stratford displaced by the Olympic park. After this comes a tour of the building itself.
To add to the mystery of this largely unseen cavern of transport wonder, instructions on how to join the event will only be provided when you book.
Visiting times for the bus garage are 9.45am or 1pm on 28 June. Tickets still available at time of writing cost £10/£8 and must be pre booked here.