Given that it's an industrial city and business center that's also rich in natural beauty, there are many things to do in Monterrey. A top attraction is the old town, which dates to the 18th century and is home to many old houses, mostly built from ashlar; some of its major streets are cobblestone.
Macroplaza is one of the largest plazas in the world and houses the main government buildings, museums, the city's theatre, and the Central Library. If you're new to town and looking for what to do in Monterrey, this is a good place to start. The plaza also has gardens -- the Fountain of Life and the Faro del Comercio, one of the most monumental things to see in Monterrey.
Other attractions in Monterrey include museums such as the Monterrey Metropolitan Museum, the Museum of Contemporary Art, the Museum of Mexican History, and the Regional History Museum in the Palace of Obispado. In terms of stuff to do in Monterrey that involves the outdoors, we can't forget to mention that Monterrey is known as The City of Mountains -- the city is ringed by tall peaks.
Other Monterrey activities and Monterrey attractions include a visit to the numerous natural areas, including the Cerro de la Silla, El Cerro de las Mitras, and La Sierra Madre, where the famous area known as "Chipinque" is located. Other places to visit in Monterrey include the Huasteca and El Cerro del Topo Chico, famous for its hot springs.