A major feat in engineering is happening right above drivers' heads in downtown D.C.
The Capital Crossing project is creating city blocks in the air above the 3rd Street Tunnel.
"This is the first large tunnel in an urban area post 9/11," said Sean Cahill, a spokesperson for Property Group Partners.
Beams and support structures are going up at the tunnel to ensure the future buildings above are fully supported.
It's a major undertaking that has caused major disruptions to traffic for the estimated 60,000 cars that roll through the tunnel each day.
However, Cahill said traffic flow will improve once the project is complete.
New and improved entrances to I-395 are expected to help drivers, while a new city street grid should help pedestrians and cyclists.
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In about two years, the first building, 200 Massachusetts Avenue, is expected to open. The entire project is set to finish by 2020.