With 2.4 million inhabitants Mashhad is Iran's second biggest city and one of the holiest cities for Shia Muslims. Mashhad lies in eastern Iran, not far from the borders to Afghanistan and Turkmenistan, about 730 km to the east of Tehran, in the Razavi Khorasan province. The main attraction of Mashhad is the Imam Reza Holy Shrine, also known as Haram-e Razavi, or Haram complex. This is a pilgrimage centre extending over an area of 500m x 500m with several courtyards, beautifully decorated halls and other structures. Mashhad is a clean and modern city with a good infrastructure. It has an international airport and is connected by train to Tehran. A metro system is in operation and is being expanded. Mashhad is centre for higher education with over 20 colleges and universities.