Folly Brook

Folly Brook is a 2+1⁄4-mile (3.6 km) long brook in the London Borough of Barnet. It is a tributary of Dollis Brook, which is a tributary of the River Brent, which is a tributary of the River Thames. Folly Brook is lined for most of its length by narrow strips of woodland and scrub, with a good variety of trees and shrubs. It is one of the best streams in Barnet for small aquatic invertebrates, including several species of caddis fly and a stonefly, which are only found in unpolluted waters.