The Fleet River is a subterranean river that flows beneath London from Hampstead Heath to the Thames. Though now hidden to the world above, the river used to provide fresh spring water and hydro-power for industry until the 1700’s, when it was buried due to a series of cholera out-breaks. Presently there are plans to return the river to the surface as it is no longer used as a sewage overspill. The Fleeting Glances project however considered retaining the Fleet in its brick Victorian tunnels and instead activating the space through a series of interactive and lanterns along its route. Using an internal counterweight system, these lanterns were designed to activate when water was poured into an opening. As the water slowly filtered out of the counterweight system, the lamp would close, returning the path just taken to darkness.