followed classical Persian architecture featuring domes and colossal arches. The oldest surviving Qutb Shahi structure in Hyderabad is the ruins of the Golconda Fort built in the 16th century. Most of the historical bazaars that still exist were constructed on the street north of Charminar towards the fort. The Charminar has become an icon of the city; located in the centre of old Hyderabad, it is a square structure with sides long and four grand arches each facing a road. At each corner stands a -high minaret. The Charminar, Golconda Fort and the Qutb Shahi tombs are considered to be monuments of national importance in India; in 2010 the Indian government proposed that the sites be listed for UNESCO World Heritage status. Among the oldest surviving examples of Nizam architecture in Hyderabad is the Chowmahalla Palace, which was the seat of royal power. It showcases a diverse array of architectural styles, from the Baroque Harem to its Neoclassical royal court. The other palaces include Falaknuma Palace (inspired by the style of Andrea Palladio), Purani Haveli, King Kothi Palace and Bella Vista Palace all of which were built at the peak of Nizam rule in the 19th century. During Mir Osman Ali Khan's rule, European styles, along with Indo-Islamic, became prominent. These styles are reflected in the Indo-Saracenic style of architecture seen in many civic monuments such as the Hyderabad High Court, Osmania Hospital, City College and the Kacheguda railway station, all designed by Vincent Esch. Other landmark structures of the city constructed during his regin are the State Central Library, the Telangana Legislature, the State Archaeology Museum, Jubilee Hall, and Hyderabad railway station. Other landmarks of note are Paigah Palace, Asman Garh Palace, Basheer Bagh Palace, Errum Manzil and the Spanish Mosque, all constructed by the Paigah family. Economy Recent estimates of the economy of Hyderabad's metropolitan area have ranged from 40-74 billion (PPP GDP), and have ranked it either fifth- or sixth- most productive metro area of India. Hyderabad is the largest contributor to the gross domestic product (GDP), tax and other revenues, of Telangana, and the sixth largest deposit centre and fourth largest credit centre nationwide, as ranked by the Reserve Bank of India (RBI) in June 2012. Its per capita annual income in 2011 was . , the largest employers in the city were the state government (113,098 employees) and central government (85,155). According to a 2005