The famous Rainbow Tunnel is today's Photo Of The Day. Taken by UrbanToronto forum member brewster, it is the first photo in a pretty cool photo thread that spotlights Don Mill then and now. 

Image by brewster

Now technically the tunnel is just outside of Don Mills. It can be seen from the northbound Don Valley Parkway as you approach Lawrence Avenue. But it leads to Don Mills. And it leads to the following Don Mills then and now photos.

Image by brewster

Image by brewster

Image by brewster

Image by brewster

Find the full thread with many more pictures here.