Three physical features dominate Azerbaijan: the Caspian Sea, whose shoreline forms a natural boundary to the east; the Greater Caucasus mountain range to the north; and the extensive flatlands at the country's center. There are also three mountain ranges, the Greater and Lesser Caucasus, and the Talysh Mountains, together covering approximately 40% of the country. The highest peak of Azerbaijan is Mount Bazardüzü (4,466 m), while the lowest point lies in the Caspian Sea (−28 m). Nearly half of all the mud volcanoes on Earth are concentrated in Azerbaijan, these volcanoes were also among nominees for the New7Wonders of Nature.