Mashhad (Persian: مشهد) is the second largest city in Iran and one of the holiest cities in the Shia Muslim world. It is located 850 kilometres (530 mi) east of Tehran, at the center of the Razavi Khorasan Province close to the borders of Afghanistan and Turkmenistan. Its population was 2,427,316 at the 2006 population census. It was a major oasis along the ancient Silk Road connecting with Merv in the East.