Cuba is the largest island in the Caribbean and separates the Gulf of Mexico from the Caribbean Sea. Forming the choke point for shipping routes out of the Gulf of Mexico to the Atlantic and Pacific oceans, Cuba is a strategically significant territory in the Western Hemisphere. Cuba lies in a subtropical humid zone with mostly flat geography that is well suited for agriculture, such as sugar, coffee and tobacco. Havana is the political and economic core of Cuba, with more than 2 million people, or about 20 percent of the island's population. Rugged terrain to the southeast is dominated by the Sierra Maestra Mountains, which have historically been used by individuals seeking refuge from government control. It was from this region that the Cuban revolution of 1959 was planned and executed. Cuba's major geographic challenge is its proximity and importance to the United States. Its location has repeatedly made the island a battleground in global affairs.The Cuban Missile Crisis of 1962 was the pinnacle of conflict over Cuba, and since that time, U.S. policy has revolved around denying foreign powers military access to the island. In the wake of the Cold War, Cuba's close relationship with Venezuela has provided an important source of petroleum for the politically and economically isolated island. Cuba is emerging from its communist economic model, but with limited resources and an underdeveloped industrial sector, it will take time for the country's economic model to evolve.