Mashhad started life out as Sanabad, a village pitstop for trade caravans headed towards Turkmenistan. But in the ninth century, the eighth Shi'ite Imam Ali Bin Moosa Al Reza, the great grand son of Imam Ali who was the cousin & son in law of Prophet Mohammad was poisoned by the jealous caliph of the time. Imam Reza was buried in Mashhad, and his shrine became one of the holiest sites to the shi'ite muslims after the Holy Kaaba in Saudi Arabia and Karbala in Iraq.Over the next thousand years, the shrine complex was levelled, ransacked and rebuilt a number of times depending on the ruling army of the day. Today the Shrine is the most important place in the city and in the whole of Iran.The love & respect for the Imam in this city is so immense that every person, taxidriver, shopkeeper, whoever he is, will go out of the way and help any newcomer who wants to visit the holy Shrine and is seeking any assistance.Also keep in mind that city is very conservative by western standard in so many ways. Dress code for women is very strict however a self encompassing '''chador''' is not a must for any lady in public place in city but is a must in holy shrine. In the vicinity of the shrine even men with shorts, if there are any, will get stern looks from the locals. Respect the dress code and then be assured of any help if required.Photography inside the holy Shrine is not permissible as all visitors will be frisked at the various gates leading to the Shrine. There are separate entry gates for ladies and gents. http://wikitravel.org/en/Mashhad