A city classic that's always packed at lunchtime, but just squeeze onto the end of one of the benches and tuck into the house special: tián shuĭ miàn, which is a tongue-tingling, mind-blowing bowl of thick, sugary noodles in a spicy sauce. Try it once and you'll come back day after day.
Don't expect to linger after eating here: this is a hot, sweaty, in and out kind of place with no time for small talk.