Not too many years ago, the East Veterans Memorial Building at Wellington and Lyon (built 1949-1956) was renovated, and received some upgrades. However, I only recently noticed that these renovations included a modern office extension of the building on the top floors. On the ground, you can only see the new upper floors from the west side of the Lyon Street sidewalk, all you see from Sparks Street is the original building:
An excellent demonstration that you don't need to stick a 20-storey tower on top of a heritage building to modernize it!
There is a report on the seismic rehabilitation (PDF - Google html preview here)
[Look for more one-photo posts under the label Singles]