For the scientific intellectuals among us, here is a short explanation of how the "Curious Rocks" came to be...
Little Round Top at Gettysburg (and its higher and more wooded southern neighbor, Big Round Top) is underlain by York Haven-type diabase (early Jurassic) of the northwestward-dipping Gettysburg sill. Physical and chemical weathering along joints and non-systematic fractures has created rounded boulders and cobbles ranging in size from a foot or less to twenty feet or more. A great tourist attraction, most striking of the weathering phenomena is the arch formed by the "Curious Rocks."