Summit of Alba Patera. This volcano is only a few kilometers above the surrounding plain which, coupled with its large diameter of some 1700 km, gives it a much lower profile than the Tharsis volcanoes. The rim of an old caldera near the summit, partly buried by younger lava flows, is visible at the bottom left; at the bottom right a younger caldera is at the top of the youngest summit cone. Lava flows are well preserved, and flows can be seen extending from near the lower right of the picture toward the upper left. The image is about 220 km across. North is to the upper left.
Source: NASA