Multi-story car parks

Today I took our West African mechanic shopping for vehicle fluids. We parked in a multi-story car park (parking garage) two floors under a hyper-market, and it was his first experience of such a place. He couldn't believe that concrete buildings were capable of holding the weight of hundreds of cars, and walked around in awe of the place, muttering "this is strong concrete, strong concrete!" as if willing the place to stay strong whilst he was inside. Maybe he didn't quite trust it's strength. Olly