Lanzhou beef noodles — lanzhou lamian (兰州拉面) — are the defining dish of the city and one of the great breakfast foods of China. The broth is made from beef bones simmered for hours until it is clear but deeply flavored, served in a bowl with hand-pulled noodles of your chosen thickness (from thin angel-hair to flat ribbons to thick rope-like strands), sliced beef, white radish, chilli oil, and fresh coriander. A bowl costs between 10 and 20 yuan.
The dish is widely imitated across China, but Lanzhou versions are noticeably better — fresher, more precise, the broth more honest. Almost any of the hundreds of small noodle shops along the main streets will do a good job. Look for the shops that are busy at 7am and sold out by 9am — those are the serious ones. Ma Zilumanzi, in operation since 1915, is the most famous old shop and worth visiting for its history as much as its noodles.