STAFF PICK: Backed up against the foothills of the Rincon Range is a real gem in the crown of Tucson's natural treasures. Colossal Cave Mountain Park will celebrate its official grand opening as a multiservice facility this fall (the October 1 date was reportedly pushed back due to zoning problems). Not only does the park offer an opportunity for subterranean adventure, but visitors can also ride horseback along the trails of the historic Posa Quemada cattle ranch. A two-mile nature trail (complete with docents), a complete research library and gift shops round out the park's prospective offerings. As if these supplemental attractions aren't enough, the cave itself is a downright magical hunk of Sonoran Desert terrain, powerful enough to replenish the soul all by its lonesome.