UPDATE: The Endless Stair has been moved to Tate Modern.
Sure to be one of the highlights of this year's London Design Festival is the Endless Staircase on the south side of St Paul's Cathedral.
The Escher-emulating timber construction is the invention of architects dRMM and engineers Arup, and comprises 24 interlocking flights of stairs, which the public will be able to climb for an elevated view of the surrounding area and south toward Millennium Bridge. It will be illuminated at night by a custom-designed lighting scheme.
LDF has prior form when it comes to staircases and St Paul's: two years ago John Pawson installed an optical illusion within the cathedral's lesser-seen Geometric Staircase.
London Design Festival runs from September 14-22.