It is one of the most man-made spaces on the planet, but everything in New York from the height of the skyscrapers to the way the subway was constructed to the position of the harbor is governed by the extraordinary forces that ultimately shaped this city. You can tell the geology of Manhattan at a glance by looking at the skyline. The skyscrapers of Midtown and Downtown are built on hard granite; the low-rise buildings in between are built on a soft, gravelly soil left over from the Ice Age. Learn how New Jersey and North Africa were neighbors 250 million years ago, how the rocks New York are built on are the remains of mountains that 450 million years ago were as tall as the Himalayas, and how Long Island is covered in rubble that remained as ice sheets retreated 10,000 years ago.