We got on the U-bahn, the city's underground rail system, and headed to the Iranian embassy to inquire about visas. Together with the S-bahn, which travels above ground, the U-bahn is cheap and fast way to get around the city. Interestingly, tickets are required but there is no entrance and exit checkpoints or turnstyles to go through. Hamburgers are trusted to buy the correct ticket, and if you are caught traveling without one, the fine is very steep.