How is this possible?

Hello everyone. I came across this site at http://percypea.co.uk/gta/ and was blown away by how the buildings are 3d like. I LOVE this effect! BUT I have no idea how to do it!

I have experience building tile maps, like this one, but no 3d experience what so ever - but I do have a general idea on how it works . I was wondering if anyone could offer some help on how to do 3d effect on/using a tile base map like this one. I assume its different for stand along 3d rotate the cube tutorials all over the place, but then I am not too sure.

I know it isn’t using papervision because the textures on the side of the building are smooth and don’t get jagged any time, unlike papervision’s.

Please help with this… I really want to do something like this