Looking for downtown’s professional set during the week? Forget finding them at the crosswalks—the real action is 20-feet below, in the 7.5-mile-long tunnel system.

Although the multi-block tunnel system wasn’t initially created to connect Downtown’s skyscrapers, the evolution of each section provided a welcome navigation option for downtown employees looking to avoid inclement weather. The series of subterranean passages, each owned and maintained by the building they sit beneath, allows the district’s 150,000-employee workforce to take on tasks—doctors appointments, banking, shopping, post office and salons, among other things—in air-conditioned bliss.

Access the network via street-level stairs, escalators, office-building elevators or head to Wells Fargo Plaza, which offers direct street-to-tunnel access. The Tunnel System is open Monday through Friday from 6 a.m. to 6 p.m. You can also take a guided tour of the tunnels with a local company.