Fun Project - Photoshop new buildings into an old painting

Manchester University @ Poussin's Colosseum

the original painting can be found at http://www.masterart.com/Jean-Lemaire-called-Lemaire-Poussin-Dammartin-Go%C3%ABle-159-The-Colosseum-with-Artist-sketching-PortalDefault.aspx?tabid=53&dealerID=384&objectID=432802 Thanks