Arizona - Organ Pipe Cactus National Monument

In southwestern Arizona, on the frontier with Mexico, is Organ Pipe Cactus National Monument, in which are three distinct desertic vegetation zones with some 30 different species of cactus, in particular the characteristic organ pipe cactus, up to 23ft/7m high, which blooms from May to July but because of the great heat during the day opens up its flowers only after sunset. The area can be explored on various roads and hiking trails.

There are two scenic drives of note. The Ajo Mountain Drive and the Puerto Blanco Drive.