This Traveltalk series short visits three cities in Mexico. We start in the village of San Miguel de Allende, known for its churches. A monastery has been converted to a school of arts. The second stop is Queréaro, where a 5-mile-long aqueduct built hundreds of years ago is still functional. It was near this city that Emperor Maximilian was executed in 1867. Then it is on to Monterrey, the large industrial city whose nickname is the Pittsburgh of Mexico. Here are steel mills, other factories, and the largest brewery in Latin America.