As underground engineering consultancies go, Italy's Trevi Group is no joke; they're the folks that were hired to stabilize the Leaning Tower of Pisa in the 'aughts.
And back in the '90s (if you couldn't tell by the quality of the images below), they were tasked with designing a more efficient underground parking system in Cesena, Italy. Your average underground parking garage takes up a lot of space that cars cannot be parked within; you need lanes and ramps for access, and that takes up room and requires a lot of concrete. To solve this, Trevi instead devised a concrete cylinder, nine stories deep, with each level able to store 12 cars in a clock-like array.
The cars are deposited and served up by an automated lift-and-trolley system:
Today there are 16 Treviparks, as they're known, in Europe and Scandinavia. "Trevipark can be located in courtyards and garden areas with entrances at floor level or underground," the company writes, "without compromising the environment of the area concerned. The reduced sizes of the entry-and-exit bays make Trevipark environmental impact negligible."
"Internal safety of the car is assured by the anti-intrusion, fire-fighting, anti-flood and ventilation systems that are computer-controlled. In turn, the computer is connected to the Trevipark's control centre operating 24 hours a day."