Part of the Great Fen Project - Holme Fen is situated south of Peterborough, around 5km north-west of Woodwalton Fen and on the south-western shore of the former Whittlesey Mere.

The Fen occupies a crescent shaped site approximately 2.5km long by 1.5km wide and has been designated as a Site of Special Scientific Interest (SSSI) and Geological Conservation Review Site (GCR).