Invisible lift

An invisible lift allowed transportation between Torchwood Three and the Roald Dahl Plass above. Torchwood personnel could enter or leave without arousing suspicion, since the exit benefited from the effects of a perception filter.

Functions
The invisible lift had the appearance of a slab of concrete next to the water tower. When someone stepped on it, they would become unnoticed by anyone. It could be remotely activated by Jack's vortex manipulator. (TV: Everything Changes)

The lift had what Toshiko Sato referred to as a "design fault"; when it rained, water would fall in through the open slab. Leaves and birds would also sometimes fly into the hub through the hole. (PROSE: Another Life)

History
As Jack Harkness would explain to Gwen Cooper, Torchwood had "no idea" how the invisible lift worked though they knew how to use it. However, Jack suggested that a dimensionally transcendental chameleon circuit, when placed on the spot, had welded its perception properties to the spatio-temporal rift. (TV: Everything Changes) Indeed, Jack had been present in one instance where the Doctor's TARDIS landed on Roald Dahl Plass, where it used the rift to refuel. (TV: Boom Town)

The invisible lift existed as early as 26 March 2005, when it was used by Torchwood One director Yvonne Hartman to enter the hub, which was temporarily frozen by a time bubble operated by Rajesh Singh, so she could procure a Drahvin scanner from the hub unhindered. (AUDIO: One Rule)

While showing off Torchwood, Jack took the invisible lift with Gwen (who pointed out the someone could fall in the hole when the lift was being used). He used it again to stop Suzie Costello from killing Gwen, but the perception filter failed to work on her, allowing Suzie to shoot Jack. (TV: Everything Changes)

When Lisa Hallett was activated, the team used the lift to escape, allowing Myfanwy to fight Lisa. (TV: Cyberwoman)

Jack used the lift to enter the hub with John Hart. (TV: Kiss Kiss, Bang Bang)

Gwen introduced Rhys to Torchwood by using the lift. (TV: Meat)

When Agent Johnson planted a bomb inside Jack, Ianto and Gwen used the lift to escape. The lift was later destroyed along with the Torchwood Hub. (TV: Children of Earth: Day One)