OKLAHOMA CITY (AP) — Underneath the streets of downtown Oklahoma City, a series of tunnels connects parking garages and office buildings. What many don't know is that the tunnels also contain a small collection of businesses and restaurants.

Oklahoma City's underground tunnel system is nothing new. The first tunnel was built in 1931 by W.B. Skirvin to connect the Skirvin Hotel with the Skirvin Tower — now 101 Park — across the street.

The majority of the current tunnel system was built in the mid-1970s under the leadership of banker Jack Conn and Oklahoma Industrial Authority and opened in 197...