It's not quite as busy as Bank yet, but the disused station Aldwych opens with increasing regularity these days. In September it hosts Lost and Found: A Secret Underground Journey, an immersive theatrical event that tells the story of the network's 150-year history.
The 75-minute tour, which will be illuminated with video, audio and interactive installations, will take visitors into the station's ticket hall and down onto the platforms, which haven't welcomed paying commuters in nearly 20 years. Tickets cost £25 for off-peak, or £30 for peak times, with a £5 discount on both for concessions (note that the Museum's booking site doesn't work with Chrome, iPads or Macs). Time Out is also offering discounted tickets.
Each ticket includes entry to the London Transport Museum, which is currently showing the wonderful Poster Art 150, featuring some of London Transport's greatest poster designs.
Closed in 1994, Aldwych was a spur on the Piccadilly line south from Holborn. Nowadays it is used for film and TV productions, and it has in recent years been used for site-specific opera and for a Blitz-themed event.