Airport – Marine Drive
If you are staying near the airport, there are a couple of options, one further of a drive than the other. A 3/4 mile bike path down Airport Way from the terminal will bring you to Marine Drive. Marine Drive is a 12 mile long bike path that runs along the Columbia River on the northern border of the city. As opposed to the more scenic routes in Portland, Marine Drive is completely flat. Depending on whether you travel east or west, you will traverse some bridges. A 6 mile route has been included above as an example.
If you are near the airport and want to get out a little further, Blue Lake Regional Park is a public park 10–15 minute drive west of the Airport, along the coast of the Columbia River. Its 101 acres boast bike paths, wetlands, and the titular lake, which is formed from underground springs. There is very affordable parking. Follow the bike paths for runs ranging from 3 – 7 miles, or even longer, if you so choose. For more information about the park, visit its website.