Work is underway on a 1km-long cycle track on the site of a lake next to Doncaster Dome.
Builders have already drained the lake next to the leisure centre, and diggers are now well on with earthworks at the site.
The building site is fenced off and yellow construction vehicles can be seen on the site, which now looks like mud.
When it is completed, the 1km-long circuit is expected to attract more than 40,000 cyclists a year and experts see it as a way of getting more people more active.
A report to planners when planning permission for the scheme was put to the council said the track will cater for the existing and growing numbers of recreational cyclists, particularly providing a safe traffic free environment for young people and adults to Doncaster Dome develop their skills.
The track would wind around the car park and use some of the land taken up by two lakes.
It is understood that fish have already been relocated from the lake which was previously on the site.
Concerns were raised before the scheme was approved about the effect building the track would have on wildlife habitats.