Polo is Uyghur rice pilaf, and it is one of the great dishes of Central Asia. Lamb — usually on the bone — is braised with carrots, onions, chickpeas, and raisins in large cast-iron pots, then the rice is added to absorb all of that fat and sweetness. The result is dense, aromatic, and satisfying in a way that holds you through an afternoon of walking. It is lunchtime food: the pots go on in the morning and are ready by noon, and by mid-afternoon the good stuff is usually gone.
In the Erdaoqiao area, look for restaurants where a large pot sits visible near the entrance — this is both an advertisement and a sign of confidence. The most atmospheric spots are the simple ones: long communal tables, rice served by the ladle, a plate of sliced tomato and cucumber on the side. Some restaurants add boiled eggs or dried fruit on top as a garnish. Polo is the kind of food that requires little ceremony, and the best places understand this. Come hungry.