The area of modern-day Saudi Arabia formerly consisted of mainly four distinct historical regions: Hejaz, Najd, and parts of Eastern Arabia (Al-Ahsa) and Southern Arabia ('Asir). The Kingdom of Saudi Arabia was founded in 1932 by King Abdulaziz (known as Ibn Saud in the West). He united the four regions into a single state through a series of conquests beginning in 1902 with the capture of Riyadh, the ancestral home of his family, the House of Saud. Saudi Arabia has since been an absolute monarchy, effectively a hereditary dictatorship governed along Islamist lines. The ultraconservative Wahhabi religious movement within Sunni Islam has been described as a "predominant feature of Saudi culture", although the power of the religious establishment has been significantly eroded in the 2010s. In its Basic Law, Saudi Arabia continues to define itself as a sovereign Arab Islamic state with Islam as its official religion, Arabic as its official language, and Riyadh as its capital. Saudi Arabia is sometimes called "the Land of the Two Holy Mosques" in reference to Al-Masjid al-Haram (in Mecca) and Al-Masjid an-Nabawi (in Medina), the two holiest places in Islam.