It’s a tunnel !
Several folks correctly guessed this one with Lois being the 1st correct reply, followed by several others who remembered our recent road trip.
This view is inside one of the 2 tunnels of the Chesapeake Bay Bridge Tunnel (CBBT).
We went through the CBBT on our recent road trip to Portsmouth, VA to see the summer love tour of A Prairie Home Companion.
The CBBT measures 17.6 miles (28.4 km) and is considered the world's largest bridge-tunnel complex. The span includes over 12 miles of low-level trestle, 2 mile-long tunnels, 2 bridges, almost 2 miles of causeway, 4 manmade islands and 5-1/2 miles of approach roads, totaling just over 23 miles.
The official name of this span is the Lucius J. Kellam, Jr. Bridge-Tunnel as of August 1987, but we’ve never heard refer to it that way.
Kellam spearheaded the project and served as a member of the Chesapeake Bay Bridge and Tunnel District and Commission for over 40 years.