A host of new measures designed to cool the Tube network over the summer months have been announced.
Mayor Ken Livingstone warned the trials could take years
But London Mayor Ken Livingstone warned that the £150m investment in heat reduction schemes would "take years to deliver results".
The multi-million pound pilot programme includes using cold water from an underground river at Victoria station.
A new mechanical chiller will also be installed at Oxford Circus station to provide cool air to the ticket hall.
The Mayor said: "London's Tube network is the oldest in the world and its design makes cooling the system extremely difficult.
"Transport for London is pushing forward a programme to tackle the problem of heat on the tube, after the decades of underinvestment."
Later this year, work will start on a trial at Stockwell station that will involve drilling a borehole to the water aquifer below ground, where cold water will be extracted and used via a heat exchanger to cool warm air.
The warmed water will then be returned to the aquifer.
Temporary portable industrial fans will be trialled at Seven Sisters and Chancery Lane stations this summer to increase air circulation and if successful will be rolled out to a number of stations in 2008.
The £150m expenditure by Transport for London to reduce heat on the network during the summer months is part of an overall £10bn investment programme on the Tube.