Sangumburi (산굼부리) is a crater with a circumference of over 2 km, and has been designated as a Natural Monument. It is located on the southeast side of Jeju-si, and is a flat crater, about 650 meters wide, 100 meters deep, and 2,070 meters in circumference. If you look at the crater from above up, it looks like a man-made circular stadium. There is a variety of plant-life in the crater. On the north side, Nandaeseong vegetation such as red-thorn trees, and magnolia trees grow, along with the rare winter strawberries. On the south side of the crater, Ondaerim vegetation such as evergreens, maples, and mountain strawberry trees cover the area. Because so many different kinds of trees and plants grow in such a limited space, it attracts the attention of researchers as well.