Kempton Great Engines. London

The Kempton triple-expansion engines are situated in Hounslow, West London, at a water treatment site. They were formerly used for pumping drinking water to a reservoir, but ceased operation in 1980, when the building and contents were declared a Grade II* listed monument. The site is now leased by Thames Water to a preservation trust.
One of the engines is in working order, and the other under restoration. These are the biggest engines of their type ever erected in Britain, and the working one is the biggest triple-expansion engine in the world still operating. Each stands 62 feet high, weighs around 1000 tons and generated 1008 Hp.
The handsome engine house is original and the walls are covered internally with glazed tiles. The colossal engines are still in their original positions, as are two steam turbine pumps and much ancillary equipment. One of the big engines is run on steaming days. There is a lot to look at, and you can get a guided tour to climb up on the non-working engine. This place really deserves to be much better known.
If visiting by road, the site is signed from the roundabout under the A316. Beware the speed bumps. Parking is under the flyover.
On an adjacent site is the self-described Hampton to Kempton Waterworks railway. This is a project to recreate the narrow-gauge railway that supplied coal to the site. So far, it consists of a loop of track in an adjacent field, and a steam engine and carriage. You can ride on it.