Part of the villa's system of underground traffic tunnels, the Grand Trapezio's four sides form a trapezoid with two North-South branches that are 304 m long and two East-West branches 296 m long. The tunnels were only wide enough for one-way traffic. As the provisioning of the Villa progressed, these tunnels were used for parking the empty carts far from the loading areas in preparation for the changing of the direction of traffic in the tunnel. The tunnels formed a loop so that vehicles did not have to back up. Stalls were provided for the horses, donkeys, and mules. The theory that the tunnels were used as a place for religious ceremonies is improbable. The tunnels date to the first years of Hadrian's development of the site.