The Sierra Negra crater is is 6.2 miles (10 KM) across and it is the second largest caldera in the world next the Ngora Ngora crater in Africa. It, along with I think 4 or 5 other volcanoes, created Isabela Island, the largest of the Galapagos. I am standing near the edge of the crater and what you see out in the distance is the flat frozen lava field and eventually the ridge of the other side of the crater.