This ladder has been featured before, but I get quite often mail with pictures of it, and I love it so I post it again. I like it so much that it even is on the cat-ladder Hall Of Fame.
Thanks to Steven McDonald who sent the picture this time!

And now for the best! The sender Kami77 wrote in the comments on July 30 this year, exactly where the stairs are!

"The one in Montreal, Canada is actually in Québec City, Canada. My collegue lives right there. Look for "877 Rue de Claire Fontaine, Quebec City, Quebec, Canada" in Google Maps and go to Street View. Turn until you see a parking spot with a grey Honda. You'll see the cat staircase right there."

Has posted a print screen below, and a link directly to the site so you can walk around in the neighborhood!