Mashhad is considered a holy city, where saints are buried. We planned to spend a few days but soon found that whole parts of the city were closed to us. There were no signs or warnings. If we wanted to enter a part of the city that, unknown to us, was closed to foreigners, a crowd of people would quietly but suddenly block access. It was not violent, but it was decisive. We never were able to see any of the religious sites of Iran.