The city sits in a saddle between the two mountains Machu Picchu and Huayna Picchu, with a commanding view down two valleys and a nearly impassable mountain at its back. It has a water supply from springs that cannot be blocked easily. The hillsides leading to it were terraced, to provide more farmland to grow crops and to steepen the slopes that invaders would have to ascend. The terraces reduced soil erosion and protected against landslides. Two high-altitude routes from Machu Picchu cross the mountains back to Cusco, one through the Sun Gate, and the other across the Inca bridge. Both could be blocked easily, should invaders approach along them.