The treasury was looted by Afghan invaders in 1735 and rebuilt by later kings. It was made collateral for government liabilities to the national bank in 1937 and later transferred to the central bank in its present vault in 1960. The best connections are from Dubai, United Arab Emirates, with daily flights. The language is Farsi, and few people speak English. Most businesses, banks, offices, embassies and shops are closed on Fridays, the Muslim sabbath.
Summers can be unbearably hot in Tehran.
Avoid visiting Iran during the Islamic fasting month of Ramadan, which varies from year to year. The second half of March, when Iranians celebrate the Persian New Year, is an equally difficult period to get accommodations and transportation. In winter, take a heavy coat, hat, scarf and boots to negotiate heavy snow. A guidebook and a Farsi-English phrasebook will be invaluable. One dollar equals about 3,000 rials in banks, but a dollar fetches about 8,000 rials in the open market.