This image of the giant peak was released yesterday by the European Space Agency. It is a composite of multiple photos taken by a high-resolution stereo camera aboard the Mars Express spacecraft in 2004, with different elevations shown in different colours. The volcano looms 8 kilometres above the surrounding landscape - almost the height of Earth’s tallest peak, mount Everest.
The thing that really makes Tharsis Tholus stand out among the other Marsian giants is its battered condition. It long ago spent its lava, leaving a gaping cavity in the centre, which is coloured here in green. The lack of support for the roof caused the walls to collapse, resulting in the leftover ridge, shown in brown in the picture.