In Pictures: Iran marks 1979 hostage crisis

Graffiti adorns the walls of the former US embassy - this one is among the few iconic anti-US murals remaining around Tehran. The compound is one square kilometre, and although part of it is preserved as a museum, most it it remains off-limits to civilians. The compound, dubbed "the den of spies", is under the supervision of the Iranian government and the Revolutionary Guard.

A woman walks past the main entrance to the former US embassy. The slogan painted on the wall after the revolution translates to, "We put America under our foot".

The former US embassy in downtown Tehran. The second floor of its main building is now a museum, open to the public on the anniversary of its seizure. The rest of the year the embassy and its compound remain closed to the public. Al Jazeera English was granted rare access inside, on the eve of the 35th anniversary of the Iranian revolution.

The main staircase of the old embassy, which leads from the lobby to the second floor, was painted over with anti-US murals eight years ago.

The winding staircase leads to a heavy, reinforced metal door like that of a vault, which can only be opened with a combination. On the floor, a doormat reads "Down with the USA" in English and "Death to America" in Farsi.

On the second floor of the embassy, students found communication equipment they said proved that the Americans were spies: telephones, encryption machines, telex machines and other types of devices. Property of the NSA, the encryption machines were used to send messages from the embassy to Washington. The presence of machines like this supported the view held among the revolutionaries: that the CIA was operating out of the embassy and influencing Iranian politics. The embassy continued to operate for eight months after the revolution until students put an end to it with the hostage crisis.

Not much has changed inside the embassy(***)s main building. Light green paint still adorns the walls, cracked and faded. Dust gathers on the windows and windowsills. The building stands as a relic.

Embassy staff could do little but watch as Iran(***)s revolution took hold and swept millions into the streets. The 1979 uprising ended 2,500 years of monarchy and replaced it with an Islamic republic.

When students managed to get through at least two vault doors, they found the shredding room, where embassy staff had been using industrial-sized machines to destroy sensitive documents. The students painstakingly set about piecing the papers back together, discovering internal memos and other documents about the embassy(***)s activities. Some of the reassembled documents have been published.

The inner room, inside the embassy(***)s vaulted floor, was where the most sensitive work in the country took place. The room was built with reinforced steel and security systems. Inside the room, machines that were state-of-the-art in 1979 now look like something out of a retro spy comedy movie.

A rotor from a helicopter downed in the failed Operation Eagle Claw hostage rescue operation sits on a tall metal stand, hovering above the old embassy wall. It is a reminder of the US(***) failed rescue attempt after a sandstorm in the Iranian desert caused a fatal collision between one of the helicopters and an aircraft, killing eight American servicemen.

The walls of the old embassy, ringed with metal spikes, were effective in keeping staff safe as the revolution swept through Iran. Students had attempted to storm the embassy three days after the revolution but security forces and Iran(***)s foreign ministry prevented it. Eight months later, the students were successful.

Graffiti on the walls of the embassy(***)s second floor, written during the hostage crisis. One written in Farsi reads, "This den of spies should be closed".

Another bit of graffiti on the walls of the second floor reads, "There is no time for imperialism in Iran anymore". A line in Farsi says, "Hail Khomeini" - referring to Ayatollah Ruhollah Khomeini, the leader of the Islamic revolution.