The great glasshouse is the centrepiece of The National Botanic Garden of Wales. It was designed by Foster and Partners and is the largest single-span glasshouse in the world. It is elliptical in plan, and is tilted south to maximise sunlight. The roof measures 99m x 55m and rests on twenty-four arches, which rise to 15 metres at the apex of the dome. The glasshouse was constructed between 1995-2000.

This modern building occupies the site of the now vanished Middleton Hall, once one of the grandest classical houses in Wales (see NPRN 17569). Surviving buildings, the service block and the stable court (NPRN 31623) have been adapted to serve the Gardens and some of the water features of the great early nineteenth century park (NPRN 86175) have been restored.

The icehouse associated with the house still lies beneath the Gardens (see NPRN 31622).

John Wiles 14.11.07; additional notes by T. Driver, RCAHMW, 19th Jan 2010.