The Feria de León is an enormous annual fair that runs for three weeks from January into February, centred on the Polifórum León fairground complex on the eastern edge of the city. It is one of Mexico's biggest events — drawing millions of visitors — and combines an agricultural show, a commercial exhibition, concerts, rodeos (charreadas), bullfights, and an amusement park into something that essentially takes over the city.
If you are in the Bajío region during January or February, the Feria is worth catching for at least an evening. The food vendors alone — roasted corn, carnitas, churros, and countless regional specialties — make it worthwhile. The major concerts feature Mexico's biggest norteño and pop acts. Accommodation in León fills up quickly during the Feria; book well in advance or base yourself in Guanajuato and day-trip in.