Herat is one of the oldest cities in the world, dating back to the time of the Achaemenid Empire in the 6th century BC. It is located in western Afghanistan, on the border with Iran. The city has a population of about 436,000, and it is the capital of the Herat Province. Herat is a regional trade center and the largest city in western Afghanistan. It is also the regional center of the Afghan National Railways. Herat is known for its long and rich history, and for its cultural and Islamic heritage. The city has a number of historic mosques and madrasas, as well as bazaars and a fortress.