The I-205 bike trail is part of Portland's system of bike trails. It stretches between the Clackamas Town Center shopping mall in the south to just north of the Glenn Jackson Bridge in the North. As the name implies, it runs alongside I-205.
The bike trail is a good way to get from one place to another, but it may not be the ideal spot for scenic touring, as well as perhaps being a bit unsafe. There are large stretches where the trail is uninterrupted, but at certain places, it crosses some fairly busy streets, many full of cars that just exited the Interstate, and therefore may not be going fast and not looking for pedestrians or cyclists.
Another downside is that for the most part, neither I-205 or the outer east side of Portland are extremely attractive areas, and together with having to dodge traffic, would make this a less than relaxing run. However, it is at the very least a good place to cycle to get from one place to another, as well as intersecting the Spring Water Corridor trail, which does go to some very attractive places.
Along the Glen Jackson Bridge, which the trail runs down the center of, there is around 2 or so miles of totally unobstructed trail. Since this bridge also drops a considerable distance from the northern to the southern edge, it is possible to get going very fast with very little effort, and to race down the freeway bridge between the north and southbound lanes of traffic, which can be quite a thrill.