Hi,
New Mapillary imagery shows the pitch surface is gone with trees and grass planting around the raised banks. 
https://www.mapillary.com/app/?pKey=784146193112513
Bing has reasonable resolution but no planting, with Maxar and ESRI no different. Lots of Strava heatmap data shows only asphalt path usage.
My suspicion is the original idea was an amphitheatre using spoil, the pitch didn't get maintained, and now it's general parkland.
I've added in the planting and banks from both memory, and imagery as visits to Falkirk haven't given time for survey in this direction (only more Mapillary driving imagery).

https://www.openstreetmap.org/changeset/137613243
Happy Mapping,

James