A swimming pool suspended 35m (115ft) above the ground and forming a bridge between two buildings has opened as part of a residential project in Nine Elms, south-west London, UK.

Designed by HAL Architects, the 25m Sky Pool spans two buildings at the Embassy Gardens development, located opposite the new US Embassy.

The pool has transparent walls and floor, which allows passersby to observe the swimmers – and those in the pool to see the ground.

The pool is constructed in clear acrylic. The sidewalls of the pool are 180mm thick and 3.2metres deep. Its base is 360mm thick and the whole pool weighs 50 tonnes and contains a total of 150tonnes of water, 100tonnes of which is carried by the acrylic ‘bridge’.

Because of its size, Sky Pool has been constructed in separate sections with transparent bonded joints cleverly designed to maximise the bond area and avoid areas of high stress.

HAL Architects describes Sky Pool as a "world-first".

"Sky Pool is made of crystal-clear acrylic and is located 10 storeys up, between two apartment buildings," the architects said.

"There is nothing else like it."

Specialist pool and spa consultant Devin Consulting was responsible for the water engineering on the project while wet area specialist Barr + Wray designed, supplied and installed the filtration system for the unique pool.

The inspiration for the design – for which Hal partnered with Eckersley O'Callaghan (Structural Engineering) and Reynolds Polymers (Fabrication) – came partly from the Barton aqueduct, a celebrated piece of Victorian engineering which is credited with being the first navigable aqueduct to be built in England.

According to Eckersley O'Callaghan, the team faced "significant engineering challenges" which needed to be addressed in developing the structural solution for the pool.

"The pool structure has a clear span of 15m between the buildings," Eckersley O'Callaghan said.

"The sidewalls form deep beams capable of spanning this distance whilst carrying the weight of the water, as well as resisting the hydrostatic water pressure on the sides and the wind loads.

"The two buildings are subject to normal movements, which are inherent to buildings of this scale including wind sway and foundation settlement.

"The pool structure deals with these movements by avoiding rigid connection at both ends; it slides on bridge bearings whilst maintaining water tightness.

"An additional 5m length of pool sits over the buildings at each end to make a total length of 25m.

"These parts are constructed in stainless steel and tied together across the acrylic by two high strength, spring-tensioned, stainless steel rods 38mm in diameter which sit beneath the pool."

Access to the pool is restricted to residents of Embassy Gardens and their guests.

As well as the pool itself, the project includes two "rooftop experiences", called the Orangery and Sky Deckrest, where residents can relax and socialise.

The Embassy Gardens project was developed by EcoWorld Ballymore.

To find out more about Sky Pool, click here.