This wildly undulating, 304-hectare nature reserve just west of Lyme was formed by massive landslides. They've left a challenging hiking landscape of slipped cliffs, fissures and ridges, where paths snake between dense vegetation, exposed tree roots and tangles of brambles. The Undercliff starts a mile west of central Lyme Regis; follow footpath signs from Holmbush Car Park.
One of the Undercliff's largest landslides came in 1839, when an immense section of cliffs weighing 8 million tonnes slid part way towards the sea, creating a deep chasm. The 8-mile hike between Lyme Regis and Axmouth takes an arduous four hours; alternatively walk the first mile of the reserve from the Lyme Regis end – the chalk-white bulk of Pinhay Cliffs makes a handy point at which to double back.