Guyana (pronounced /ɡaɪˈænə/ or /ɡiːˈɑːnə/), officially the Co-operative Republic of Guyana and previously known as British Guiana, is the only nation state of the Commonwealth of Nations on the mainland of South America. It is bordered to the east by Suriname, to the south and southwest by Brazil and to the west by Venezuela. It is the third-smallest country on the mainland of South America. It is one of the four non-Spanish-speaking territories on the continent, along with the countries of Brazil (Portuguese), Suriname (Dutch) and the French overseas region of French Guiana (French). Culturally, Guyana associates primarily with the English-speaking Caribbean countries such as Jamaica, or Trinidad and Tobago. Guyana can be divided into four natural regions: a narrow and fertile marshy plain along the Atlantic (low coastal plain) coast where most of the population lives, then a white sand belt more inland (hilly sand and clay region), containing most of Guyana's mineral deposits, the dense rainforests (Forested Highland Region) across the middle of the country, the grassy flat savannah in the south and finally the larger interior highlands (interior savannah) consisting mostly of mountains that gradually rise to the Brazilian border. Guyana's main mountains are contained here, including Mount Ayanganna (6,699 ft (2,042 m)) and on Mount Roraima (9,301 ft (2,835 m) – the highest mountain in Guyana) on the Brazil-Guyana-Venezuela tripoint, part of the Pakaraima range. Roraima and Guyana's tepuis are said to have been the inspiration for Sir Arthur Conan Doyle's 1912 novel The Lost World. There are also many steep escarpments and waterfalls, including the famous Kaieteur Falls. Between the Rupununi River and the border with Brazil lies the Rupununi savannah, south of which lie the Kanuku Mountains. There are many rivers in the country, the three main ones being (west to east) the Essequibo, the Demerara, and the Berbice. There is also the Corentyne along the border with Suriname. At the mouth of the Essequibo are several large islands. The 90-mile (145 km) Shell Beach along the north-west coasts. Guyana is a major breeding area for sea turtles (mainly Leatherbacks) and other wildlife. The local climate is tropical and generally hot and humid, though moderated by northeast trade winds along the coast. There are two rainy seasons, the first from May to mid-August, the second from mid-November to mid-January.