06/10/2026
The idea of a massive, hidden "underground city" beneath Tucson—complete with a sprawling, top-secret tunnel network linking distant neighborhoods—is one of the Old Pueblo’s favorite urban legends.
However, the reality is a mix of Cold War utility infrastructure, massive storm drainage systems, and a lot of local folklore. There isn't a secret subterranean metropolis where people are living or hiding out of sight, but there are significant underground networks that most residents cross over every day without realizing it.
The truth breaks down into three distinct underground systems.
1. The University of Arizona Utility Tunnels
If you are looking for a true, extensive, walkable tunnel network beneath Tucson, this is it. Wrapped underneath the University of Arizona campus is 5.3 miles of subterranean tunnels connecting over 140 campus buildings.
The Legend: For decades, rumors circulated that these tunnels were built as a web of interconnected Cold War bomb shelters, or that they were home to top-secret government laboratories. In the 1970s and 80s, students frequently snuck into them late at night for high-stakes games of Dungeons & Dragons.
The Reality: They were actually built in the 1930s as a highly advanced, centralized infrastructure project. They carry high-pressure steam pipes, water mains, electrical power, and telecommunications cables. Because of the extreme heat from the steam lines, sharp machinery, and modern motion-sensor security systems, they are strictly off-limits to the public today.
2. The Cold War Fall-Out Shelters
Tucson was a major strategic hub during the Cold War. The city was surrounded by 18 Titan II nuclear missile silos, and Davis-Monthan Air Force Base was an active piece of the nation's nuclear defense strategy.
Because of this, several buildings across the city—including downtown government offices and public high schools like Rincon, Catalina, and Palo Verde—were built with reinforced subterranean basements and self-contained fallout shelters designed to shield thousands of citizens. Over time, telephone games morphed these individual, isolated bunkers into a myth that a multi-mile "underground highway" connects the high schools directly to the military base. In reality, they are completely standalone basements, most of which are now used for mundane school storage.
3. The Desert Drainage Network
The other half of the "underground city" myth comes from Tucson's massive subterranean storm drains and washes. Because Tucson experiences intense monsoon seasons that dump inches of rain in a matter of minutes, the city relies on massive concrete culverts and underground channels to route flash floods away from roads and toward the Santa Cruz and Rillito rivers.
Some of these tunnels—like the ones running beneath Tucson High School or near 4th Avenue—are large enough to walk through when dry, leading to generations of local teenagers exploring them. These drains are frequently covered in elaborate local graffiti, but they are incredibly dangerous due to sudden, unpredictable flash floods and low air quality.