The Flickr Then and Now pool is a collection of photos comparing a place about 100 years ago to the same place today. I particularly like guil3433’s photos of Montreal. Two are shown here:

The Robert Stanley Bagg mansion, Montreal 1900 and 2003

Southeast corner of St. Denis and Ontario, Montreal 1894 and 2007
After a lot of confusion I finally figured out that there are two similar groups:
Some photos show up in both groups. Some don’t.
