The tunnels in the city-beneath-the-city project connect 30 Downtown buildings in a 20-square-block area. They have been called one of the most extensive, all-enclosed pedestrian and retail systems in the country. Other US cities with underground retail and office components are Atlanta, Chicago, Philadelphia, Dallas, Houston, Minneapolis, Seattle, Duluth and Rochester, MN, Crystal City, VA, Havre, MT and Rochester, NY.

The original tunnel link, conceived by local developer and banker Jack T. Conn, was built in 1931 to allow guests at the Skirvin Hotel to avoid car traffic and safely reach the Skirvin Tower, now the 101 Park Ave. building. The remaining tunnels were developed in the 1970s. The entire system opened in 1974 at a hard construction cost of $1.3 million.

"There are few people who worked Downtown in the early '80s who did not appreciate the vibrancy of the Downtown tunnels," Alison Oshel, vice president of operations for Downtown Oklahoma City Inc., tells GlobeSt.com. "There was a food court under the Skirvin Hotel that was the hub of lunchtime crowds. There were a number of service shops and retailers, as well. But without the necessary operating budget, the tunnels fell into disrepair, not coincidentally with the oil bust and the domino effect that this created."