Originally Posted by PDXaero

My 40 mile route route from downtown portland is
eastbank esplanade south
springwater corridor east
122nd north
marine drive west
portsmouth south
portland blvd east
vancouver st south
past the rose garden and over the steel bridge back to waterfront park.

Mostly bike lanes or bike paths with only a few difficult connnections.
Fairly flat too. If you can do 25 miles with some hills you can do this 40 mile loop.