The Grand Union Canal threads through the centre of Berkhamsted, running parallel to the High Street and the railway line. Begun in 1793 as part of a network linking London to Birmingham, it was once a working artery for the coal and grain trade; today its narrowboats are floating houses and weekend hire-craft, and the towpath is one of the best walking and cycling routes in the Chilterns.
Heading east from the centre, the path crosses a series of pretty pound locks and reaches Hemel Hempstead in about four miles. Westwards leads to Tring and the canal summit at Bulbourne, an easier and prettier walk with kingfisher sightings and pubs along the way. Bring a torch and lights if you plan to ride after sunset; the towpath is unlit.