At present, my default commute is 8 miles each way. I live in a 1920's urban "trolley" neighborhood and ride the first 2 miles on quiet neighborhood streets, then through a park, which puts me onto more urban roads, all of which (on my chosen route) have designated bicycle lanes. I'll go out of my way to ride on more bike-compatible roads.

3 Season hill climb variation - 19.5 miles, 1600 feet net elevation change - I started doing this one morning a week once the Summer kicked in, and will try to continue (I need lights now). It's about 20 miles, and ascends "City Creek canyon", which has designated "car free" days in the Summer months. Here's a mapmyride link:
http://www.mapmyride.com/routes/view/40433338