The coast path then reaches St Alban's Head, just to the south of the village of Worth Matravers. Between St Alban's Head and the resort of Swanage is Durlston Country Park nature reserve. North of Swanage is the chalk Ballard Down, the eastern tip of which has been eroded to form Old Harry Rocks - a series of stacks, arches and caves jutting into the sea between Swanage Bay and Studland Bay. This headland marks the end of the Jurassic Coast World Heritage Site. Behind Studland beach, an extensive system of sand dunes have formed a psammosere, stretching for miles across the Studland peninsula. The peninsula forms one shore of Poole Harbour, one of the largest natural harbours in the world. Part of Studland beach is the National Trust's only official naturist beach. The South West Coast Path ends at South Haven Point, where there is a commemorative marker. The Sandbanks Ferry links this to the Sandbanks area of Poole on the eastern edge of the harbour.