Colne Valley Regional Park
United Kingdom
The Colne Valley Regional Park is 43 square miles (110 km2) of parks, green spaces and reservoirs alongside the often multi-channel River Colne and parallel Grand Union Canal, mainly in Hertfordshire and Buckinghamshire, with parts in the London Borough of Hillingdon, Berkshire and a small area in Surrey.
Park data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).