The Bajio is a mountainous region in central Mexico. A rich silver-mining area in the 17th and 18th centuries, the Bajio saw an explosion of fabulous wealth for the time, and the cities there grew to be large and spectacular. By the 19th century, though, the silver lodes were emptied, and the cities became depopulated. They retain their amazing architecture and traditions, however, making them a joy to visit.
Guanajuato -- imagine a beautiful valley filled with a Spanish colonial city in a three-dimensional maze of passageways, and a rim road along the clifftops. The city is considered World Heritage by Unesco. It's also home to the International Festival Cervantino, every October arts from around the world unite cultures for about 2 weeks.
Leon The city has become known by its leather works. International Airport is just outside the city and makes transportation easy to cities around like Guanajuato, San Miguel, Dolores, etc.
San luis Potosi and Zacatecas are known for having some of the best bullfights (as well as the best bulls and matadores) of any Mexican city. The bullfighting season is generally centered around the summer months. Tickets should be purchased in advance as the fights typically sell out.