Portland is a island connected to the mainland by a spit. It is essentially a large slab of Portland stone - high at the north (the "Verne" hill), and slopping south into the sea.
The South West Coast Path runs around the coast. It detours inland around the Verne, as there is no public access to its east side (its a navy port).
The Verne (hill on the north end of the island) has dramatic scenary and intresting industrial remains of quarrying and WW2 gun batteries. The fortress on the top is a prison. It has a stunning view over Chesil Beach.
Further south on the east coast is Church Ope cove, with the remains of an old railways line which runs along the east coast of Portland (access is blocked by the port, east of the prison, however)
Portland Bill at teh far south end has a light house and industrial remains.
The centre of the island contains several council estates.