The US Den of Espionage (Taleghani St; Metro: Taleghani) is all that remains of the US embassy in which 66 American citizens were held hostage for over a year; a major embarrassment that is believed to have cost President Carter his reelection. You'll know you've arrived when you ascend the steps from Taleghani metro station and are confronted with the words "Down with the USA" painted on its wall. The compound walls are now decorated with typically anti-US paintings depicting the evils of the "Great Satan" and you can still make out a somewhat battered national crest on the front gate. A bookshop near the metro station sells copies of shredded documents found at the embassy--outlining coup plots, CIA agent covers and other James Bondish details--that were laboriously glued back together by Tehrani students. The building was opened to visitors during March 2005 as the "US Democracy Fair", but appears to have closed again. Keep an eye out in case it re-opens.

If you want to drool over some truly excessive wealth, take a look at the Treasury of the National Jewels (Ferdosi St, near the corner of Jomhuriyeh Eslami Ave; Metro: Saadi; look for the heavy iron gate and rife wielding guards beside the Central Bank). For the hefty IR 30,000 admission fee you'll get to see a collection of some of the most expensive jewels in the world. Highlights include the world's largest uncut ruby, the world's largest pink diamond (the Sea of Light) and a free standing golden globe made from 34 kilograms of gold and an astounding 51,366 precious stones. An informative IR 6,000 information book is available at the ticket counter.
The National Museum of Iran  has ceramics, stone figures and carvings dating all the way back to around the 5th millenium BC.

The gigantic Mausoleum of Ayatollah Khomeini (Metro: Haram-e-Motahar) is on the southern edge of the city. The sheer size of the shrine / shopping center is enough to make the trip worth it. Entrance to the actual mausoleum, where you can see thousands of Iranians greeve their beloved former leader, is free.