Bowling Ball Beach, California:
Compared to green sand or vanishing tides, 'round rocks' don't initially sound like reason enough to visit this Californian beach. And yet, when you get down there and see the 'bowling balls' sitting like some tidy giant's game on the sand, you can't help but get a thrill. Best seen at low tide, the rocks are freakily round and freakily regular, and clustered together as if they've been placed there. The truth is, they're stubborn. The softer rock around them washed away, but these tough customers withstood the waves.