Investigators have uncovered a major example of Scottish industrial archaeology in the middle of Edinburgh.
The gasworks had been covered to create a bus depot
They have found the remains of the capital's original gasworks, which was opened almost 200 years ago.
The site, which was discovered during redevelopment of the area, lies to the east of Edinburgh's Waverley station.
Edinburgh City Council's archaeologist, John Lawson, said Edinburgh's history was more normally associated with medieval times.
The gasworks began production in 1817 when the fuel was a new discovery.
At its peak, its workforce totalled about 200.
It was partially demolished and covered over to make way for a bus depot in the 1930s.
The area is being cleared for the building of new residential and commercial properties.
Experts are spending six months examining the scene.