The Rock of Gibraltar (sometimes calle the Pillar of Hercules or by its Latin name, Calpe) is a monolithic limestone promontory located in Gibraltar, off the southwestern tip of Europe on the Iberian Peninsula. It is 426 metres (1,396 feet) high. The Rock is Crown property of the United Kingdom, and borders Spain. The sovereignty of Gibraltar was transferred to the Kingdom of Great Britain by the Treaty of Utrecht in 1713 after the War of the Spanish Succession. Most of the Rock's upper area is covered by a nature reserve, which is home to around 250 Barbary Macaques, commonly known as 'apes'; they are the only wild monkeys found in Europe. These macaques, as well as a labyrinthine network of tunnels, attract a large number of tourists each year.