Travel back 199 million years with a trip to the Jurassic Coast World Heritage Site, a 95-mile-long stretch of coastline in southern England. This stunning fossil display is known as the Ammonite Pavement, where thousands of ammonite fossils are embedded in a limestone ledge at the west end of Monmouth Beach in Dorset. Although the ammonites look rather like snail shells, these are fossils of extinct sea creatures that are more closely related to today"s octopus or squid. Britain"s Natural History Museum notes that the fossil-filled ledge is unique in the world because of the sheer number and size of the ammonites: The fossils reach up to 27 inches in diameter. If you want to check them out, timing is everything—the ledge emerges at low tide, and there are more ammonites in large rocks nearby, too.