The unique geological curiosity known as Chesil Beach is in fact not a beach but a tombolo, a thin strip of sand and shingle that joins two bits of land together. Part of the Jurassic Coast World Heritage Site, Chesil, 18 miles long, is remarkable for its pebbles that decrease in size from east to west. It's also known as the setting for Ian McEwan's novel On Chesil Beach. You can access the eastern section leading to the Isle of Portland (a peninsula) and the western section beyond Abbotsbury all year round. However, access to the central section is restricted, with its environmentally sensitive eastern side facing the shallow saltwater Fleet lagoon entirely off-limits and its western side closed April to August to protect nesting birds. The entire beach is better suited to walking and fossil hunting than sunbathing and swimming since powerful undertow makes the water dangerous (plus it's cold). There are walking and cycle trails along the rugged coastline. Amenities: parking (at five access points, £6.50 per day); toilets (at five access points). Best for: walking; windsurfing.