limestone- Rock of Gibraltar (Wikipedia)
The Rock of Gibraltar (from the Arabic name Jabal Ṭāriq جبل طارق, meaning “Mountain of Tariq”) is a monolithic limestone mountain 426 m (1,398 ft) high dominating the western entrance to the Mediterranean Sea. It is situated near the end of a narrow 9 kilometres (5.6 mi) long promontory stretching due south into the Mediterranean Sea and is located within the British territory of Gibraltar, and is 27 km north-east of Tarifa, Spain, the southwestern tip of Europe on the Iberian Peninsula. The rock serves as an impregnable fortress and contains a labyrinthine network of man-made tunnels known as the Tunnels of Gibraltar. Most of the Rock’s upper area comprises a nature reserve which is home to about 300 Barbary macaques. It is a major tourist attraction.