(Reuters) - Here are a few facts about the Azadi Tower monument that serves as a gateway to the Iranian capital of Tehran.
* The Azadi cultural complex is located in Tehran's Azadi Square in an area of some 35 acres. The tower is 45 meters high and forms the main part of the complex.
* It was designed by Hossein Amanat, who was forced to leave the country during the Iranian revolution in 1979 and now lives in Canada.
* The tower, originally built in 1971 to commemorate the 2,500th anniversary of Persian monarchy, became a symbol of freedom during and after the 1979 revolution which toppled the reigning Pahlavi dynasty. Its name changed from Shahyad Tower, or Kings Memorial, to Azadi or Freedom.
* The tower combined different phases of Iran's history and their related architectural features: the very ancient elements of the Sassanid Empire (205-651 AD) arch, and the Islamic era pointed vault. Architecture critics consider it a symbol of the modernizing era of the Shah.
* The monument was built from 25,000 blocks of white marble from the mountains of Isfahan province, cut into 15,000 unique shapes.
* Thirty years after the Shah fell, hundreds of thousands of people again marched to the square on June 15, 2009, days after President Mahmoud Ahmadinejad was reelected, protesting against his claim to victory.
Reporting by David Cutler, London Editorial Reference Unit; Editing by Sonya Hepinstall