If I had to describe Teheran by three adjectives, I would say that it is huge (8 millions), modern (ugly) and green (tree-lined streets). What is the plus of Teheran? Its people!
Northern part is richer, more similar to European cities, with big villas and gardens. Southern is poorer and more messy. There are a few small museums, most of them not very interesting: cultural offer (I mean official, institutional one) is not of much value. Still, there are things to see.