The volcanic black sand beach of Reynisfjara stretches for five kilometers (3 mi) near the town of Vik and Cape Dyrhólaey. In 1991, Island Magazine voted Reynisfjara as one of the Top 10 most beautiful beaches in the world. On the east side, the beach borders Mt Reynisfjall, which is most famously known for its beautiful rectangular-shaped basalt formations, resulting from a geological phenomenon of a volcanic eruption. Reynisfjall is a 340 m (1116 ft) high and 800 m (2625 ft) wide tuff mountain that boasts an abundance of birdlife, the Atlantic puffins in particular. At the foot of the Reynisfjall mountain, inside the basalt rock, there's the Hálsanefshellir Cave, one of the most popular and largest in Iceland.