Within the Tehran Bazaar and surrounding the outside is packed with people almost on top of each other. When my guide and I first walked towards the bazaar, we could not even walk in, and had to go around and enter through the jewelry section (which was less busy). Outside the bazaar there are a lot of vendors with food and clothing at reasonable prices.
Most of the site is less than 200 years old, and the architecture is very pretty on the outside and within. The site itself is approx. 10km of covered stores and booths, with people on all sides of you. It can be confusing and difficult to navigate through (even at the less-crowded areas) for the first-time tourist.
In 2010 I had visited the Grand Bazaar in Istanbul, and unlike there where you could easily barter with shop owners to get a great discount on almost everything, this was just not the case at the Tehran Bazaar. In one case I had bought a scarf for my wife, and the shop owner told my guide and I that it would be 250,000 IRR (approx. $10 USD on that day -- the exchange rate fluctuates fairly constantly). My guide laughed at him, and we tried negotiating down to 200,000 IRR, but he would not come down at all. I had experienced this a few times here (and I am a really good barterer). But do not let this discourage you at all -- the prices overall are still fairly cheap, and you can find almost anything here.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.