Following up on the “Architectural Challenge” from our most recent post in creating Montreal’s RESO, an underground city, they had to go to great lengths to protect the architectural heritage of the city. One of the more ambitious feats was the underpinning of an existing church, the Christ Church Cathedral. This was part of a multi-million dollar office and retail development in 1987 that included creating underground retail and parking levels. The Cathedral was supported on piles or caissons driven down to bedrock, with a grid of massive concrete beams built on top to carry the weight while excavation took place beneath. Pretty impressive!