Lahore (/ləˈhɔər/; ALA-LC: Lahor Punjabi pronunciation: [ləhoːr]; (Urdu: لاہور; Punjabi: Shahmukhi: لہور ALA-LC: Lāhor IPA: [lɑːhoːr]) is the capital city of the Pakistani province of Punjab, the second largest metropolitan area in the country and 16th most populous city in the world. It is an important historical centre in South Asia. With a rich history dating back over a millennium, Lahore is a main cultural centre of the Punjab region and Pakistan and is the largest Punjabi city in the world. One of the most densely populated cities in the world, Lahore remains an economic, political, transportation, entertainment, and educational hub of Pakistan. Lahore successively served as the regional capital of the empires of the Shahi kingdoms in the 11th century, the Ghaznavids in the 12th century, the Ghurid State in the 12th and 13th centuries and the Mughal Empire in the 16th century. From 1802 to 1849, Lahore served as the capital city of the Sikh Empire. In the mid-19th and early 20th century, Lahore was the capital of the Punjab region under the British Raj. The traditional capital of Punjab for a millennium, Lahore was the cultural centre of the northern Indian subcontinent which extends from the eastern banks of the Indus River to New Delhi. Mughal structures such as the Badshahi Mosque, the Lahore Fort, Shalimar Gardens, the mausolea of Jehangir and Nur Jahan, Chauburji Gate, and the walled city are some of the major tourist attractions in the city. Lahore is also home to many British colonial structures built in the Indo-Saracenic style, such as the Lahore High Court, the General Post Office, Lahore Museum, Lahore Railway Station, and many older universities and colleges including the University of the Punjab, Govt College and King Edward Medical University. The Lahore Zoo, thought to be the fourth oldest in the world, is also situated here. Lahore is referred to as the cultural heart of Pakistan as it hosts most of the arts, cuisine, festivals, music, film-making, gardening and intelligentsia of the country. The city has always been a centre for publications where 80 percent of Pakistan's books are published, and it remains the foremost centre of literary, educational and cultural activity in Pakistan. It is also an important religious centre as it is home to hundreds of temples, mosques, churches and shrines like Data Durbar Complex. According to the 1998 census, Lahore's population was 6,319,000. In July 2014, Index Mundi put the population of the city at 7,566,000. An estimate in January 2015 gave the population of the Lahore agglomeration as 10,052,000. It is ranked 34 in the most populated urban areas in the world and the 8th largest city within the Organisation of Islamic Cooperation. The area of Lahore has almost doubled in the last 12 to 14 years. In 2010, Lahore was ranked as a Gamma+ world city. The Guardian has rated Lahore as the 2nd best tourist destination in Pakistan after Taxila.