Staying within Seattle city limits and with limited time, this route is 2K feet of climbing in about 2 hours. Bang it out quicker with more pressure on the pedals between the hills.
View this annotated photo map at full size.
The route is from Alki Beach to Magnolia to Queen Anne and back. The pitches are moderate to very steep, with minimal cars, and a nice flow. To mix it up, take the longer loop into Discovery Park or climb the southern side of Magnolia for more tempo. At Sunset, on a clear day you may get a photo like this or like this midday
Made this map with Google Map maker and a Geocoded RSS file. Also note: those are all, on-the-ride iPhone photos. I captured the GPS with the Biologic Bike Brain app and an iPhone inside a iPhone Mount. Photos edited and mapped in Aperture 3.