Thirteen emirates make up the Arab nation known as the Kingdom of Saudi Arabia. Situated in the Middle East, it shares borders with Oman, Yemen, Jordan, Iraq, Kuwait, Qatar, and the United Arab Emirates. With 2,149,690 square kilometers in surface area, the nation ranks 12th in the world's largest countries. Overall, the region has a dry desert environment with wide daily temperature variations. The country's topography is made up of rocky center plateaus, hilly western highlands, and sandy deserts everywhere. There are more over 35 million people living there, of which about 33 percent are immigrants. With a population of more than 7.6 million, Riyadh serves as both the capital and most populated metropolis of the nation. Mecca, Medina, and Jeddah are further significant cities. King Abdulaziz International Airport (JED), which handles over 41 million passengers annually, is the biggest airport. It is therefore among the busiest airports worldwide. The airport offers connectivity to locations across the globe and is home to Saudia, the country's flag carrier. Arabic is the official language and 90% of the population is Muslim, indicating the dominance of Islam in this culture. The Islamic sharia law and customary law are combined to form the legal system. Mohammed bin Salman bin Abd Al-Aziz Al Saud, the King and Prime Minister, is the head of state and government of the monarchy. The Saudi Riyal (SAR), the official currency of the nation, is now worth 3.75 US dollars. The economy of the nation, which is primarily under governmental control, produces a GDP of about $1.9 trillion. At $56,817, its per capita income is high. Today, the petroleum and petrochemical industries still provide 90% of the government's revenue. To further lessen the reliance on oil and gas, the government concentrates on growing alternative revenue streams including the banking and tourist industries. There are several historical and natural tourist attractions in the Kingdom of Saudi Arabia. The nation is home to five UNESCO World Heritage Sites in total. Mecca, Mada'in Saleh, the Prophet's Mosque, Heet Cave, and the Edge of the World are a few of the important locations. The Hajj is the primary reason for which the bulk of travelers travel from the Arab countries.