The area bordered by Franklin Street on the north, Cushing Street on the south, Church Avenue on the east, and Main Avenue on the west contains more than two centuries of Tucson's history, dating from the original walled fortress, El Presidio de Tucson, built by the Spanish in 1776, when Arizona was still part of New Spain. A good deal of the city's history was destroyed in the 1960s, when large sections of Downtown's barrio were bulldozed to make way for the Tucson Convention Center, high-rises, and parking lots.
However, within the area's three small historic districts it's still possible to explore Tucson's cultural and architectural past. Adobe—brick made of mud and straw, cured in the hot sun—was used widely as a building material in early Tucson because it provides natural insulation from the heat and cold and because it's durable in Tucson's dry climate. When these buildings are properly made and maintained, they can last for centuries. Driving around Downtown Tucson, you'll see adobe houses painted in vibrant hues such as bright pink and canary yellow.