South of Tucson and east of Amado, the Agua Caliente / Vault Mine Trails (7 mi) provide access to the upper slopes of Mt. Hopkins by horseback, the second most prominent peak in the Santa Ritas. The Agua Caliente Trail winds along Hopkins north slopes through a cool forest of conifers, oaks, and aspens, providing good views of the Fred Lawrence Whipple Observatory on the mountains summit as well as the upper reaches of Madera Canyon and Mt. Wrightsons rocky prominence across the canyon. Off in the distance, the Santa Cruz Valley (to the west), the Santa Catalina Mountains (to the north), and the Rincon Mountains (to the northeast) stretch toward the horizon.
There are three main ways to approach this scenic area, the most direct and most demanding of which is the Very Steep/Vault Mine Trail out of Roundup Picnic Area at the end of Madera Canyon Road. This trail earned its descriptive name from the fact that it climbs 1,400 feet in a distance of a little over one half mile. This heart-thumping climb leads from upper Madera Canyon to the vicinity of Agua Caliente Saddle, where that trail branches off toward Josephine Saddle and a number of other trails that criss-cross the upper slopes of the Santa Rita Mountains.
Agua Caliente s trailhead is located in a canyon of the same name on Mt. Hopkins western flank. From that point, accessible via the Mt. Hopkins Road, the trail proceeds up a remote desert canyon toward the mountains forested upper slopes. If you arrange a shuttle in advance, a trip that stretches between this trailhead and the Very Steep/Vault Mine trailhead in Madera Canyon makes a good long day hike. A loop that doesn't require a shuttle takes you up the Very Steep/Vault Mine trail to Agua Caliente Saddle, then northeast to Josephine Saddle and back to the Roundup parking Area via the Lower end of either Old Baldy or Super Trail.
Access For Agua Caliente: Leave Interstate 19 at the Canoa Road Exit. Take the east frontage road, 3 miles south to Elephant Head Road and turn east 1.6 miles to the Mt. Hopkins Road. Drive 4.5 miles to Forest Road 183, turn north on this dirt road about 2.4 miles to the trailhead at the canyon.
Overall, Agua Caliente / Vault Mine Trail is the 15th most popular horse trail of all 49 horseback rides in Arizona.