Massive building which held a British secret
1155, rue Metcalfe
Imposing large solid building with massive columns facing the Square Dorchester is the Sun Life building. The outside is impressive but the interior (public access) is sober but this building has a very interesting story.
In the 1940s, during the Second World War, under Churchill, Britain secretly hid important value including gold in a vault in the third basement of this building. The operation was complete with success without any loss.
So, to me, you can skip the inside unless they add a vault visit:)