Scott: that's a 5-storey (at least) prison. It has a half-storey outer wall around it as well. I'm not even sure if that thing could stay in scale with the rest of the City of Carc (where the tallest building is 3-4 storey tall) and fit on one single tile. A smaller version might be required, but it would mean demolishing a number of buildings in the CoC.
I'm also not sure if it is wise to place a prison in the middle of the city. According to
wikipedia it was built as the defences for Paris, and by looking at the map, I presume when it was built, it was on the outer edge of Paris. I might be tempted to raze the amphitheatre on tile 1 instead and build the prison there. That would be a logical place for a prison.
