I stumbled across this while looking at some past projects images and is simply my favorite job-site picture ever.
This was taken while under construction on the Diagonal Mar project in Barcelona for Gerald Hines a while back.
What you are looking at is an image of the 5 story below grade parking structure for the three story retail center that was planned above it. This project was about 1/2 mile from the ocean, and the static pressure from the water below grade required them to build the structure by digging down as far as they could (within the area defined by the 7' thick concrete slurry wall). At that point they had to pour the slab at the 3rd level down to restrain the slurry walls as they were moving in 3-4 cm. a month because of the water pressure.
Then they had to excavate below the slab to create the levels below the slab, at which point the construction project looked more like a mine than a construction site.