Biking in S King County is pretty much limited to just two major trails : BPA and Interurban. While BPA trail is great for running, I personally prefer the Interurban trail for my long , easy, leisure rides. I wrote about BPA trail here, and now I want to share my experience about biking along the Interurban trail.
The Interurban Trail starts in the town of Pacific ( well, at least for me) and stretches for 14 miles, following the historic Interurban Rail Line. There are many access point along the trail. You can leave your car at a small designated parking spot, and go for a ride in both directions ( north or south). The trail connects the towns : Pacific, Auburn, Kent, Renton.
The trail is paved, nearly straight and flat as a pancake, making it perfect for beginner cyclists ( or lazy ones like me). Comparing to the Burke-Gilman trail , it's definitely less crowded ( well, at least in autumn). I wouldn't call this trail "picturesque", as it mainly passes through industrial areas and suburban lands. But it has its own "landmarks".
Riding the southern part of the trail , you never lose the sight of the majestic Mt Rainier ( especially when "the Mount is out"). Auburn's "SuperMall " is practically "on the trail " ( stop by "Sport's Authority" if you forgot something for your long ride). The imposing architecture of the Emerald Downs Race Track might be your next stop. Though, they host live racing from mid April through the end of September, nothing will stop you from making a quick stop to take a few pics. In Kent, the trail crosses over the broad Green River. During salmon season, the bridge is a popular spot among local anglers . A southern intersection with the Green River Trail occurs at Kent’s Foster Park, providing the possibility of an Interurban-Green River Trail recreational loop through the Green River Valley. In Renton, the trail provides access to the Southcenter mall ( my bad, Westfield Southcenter Shopping Mall). To the north, there is another intersection with the Green River Trail at Fort Dent Way near Fort Dent Park.
All in all, I like this trail. It's peaceful, not overcrowded, easy to ride, gives access to many food stops, opportunity for advance ( you can continue on the Green River trail "almost" to Seattle).