Work has begun to remove coal from the opencast site at Tower Colliery in the Cynon Valley.
The deep pit near Hirwaun closed in 2008 but work has begun on the opencast. It is expected to be the final stage of coal removal at the site
Tower Colliery was the last deep pit in Wales. Its life was extended after a workers' buyout 13 years earlier.
Around six million tonnes of coal on the surface is set to be taken over the next six years.
It will be taken by rail to the Aberthaw power station in the Vale of Glamorgan.
The 240 miners who ploughed £8,000 of their redundancy into the workers' buyout will share the profits as part of a joint venture with the energy company Hargreaves.
The project has been controversial among some local residents but managers at Tower say the area will be landscaped once the coal is removed.
A planning application was approved by Rhondda Cynon Taf council to extract coal from a depth of down to 165m, and is on the 480-acre (195 hectares) old washery site, and the opencast will be 200 acres (80 hectares) in size.
Tyrone O'Sullivan, the man who led the successful workers' buyout of the mine when it faced closure in 1994, has been behind the idea.
With coal at £50 a tonne the company expects an annual turnover of £50m, more than double the turnover when Tower Colliery was a deep mine.
"Tower, when we were a deep mine, had a turnover of between £18-26m. Here we are doubling it in this new, modern era for Tower Colliery," he said.
Mr O'Sullivan told BBC Radio Wales the final era for the site will be its eventual landscaping once the opencast work is complete.
"When you look around at the mountain it has been nothing but an industrial landscape for 200 years.
"We are going to turn it back to what it should be and this final era is going to do that."
Tower Colliery was bought by 239 miners in 1995, pooling their redundancy money to raise £2m, a year after it was closed down.
Experts warned them that their plan would not work, but it remained open for the next 13 years.