An ultra-prominent peak, or ultra for short, is a mountain summit with a topographic prominence of 1,500 metres (4,900 ft) or more; it is also called a P1500. The prominence of a peak is the minimum height of climb to the summit on any route from a higher peak, or from sea level if there is no higher peak. There are approximately 1,500 such peaks on Earth. Some well-known peaks, such as the Matterhorn and Eiger, are not ultras because they are connected to higher mountains by high cols and thus do not achieve enough topographic prominence.