There's a very interesting new TV show called "Off Limits" on the Travel Channel. I've seen 2 episodes so far. The basic idea is that the host goes to a city and gets permission (usually) to go to places that most people are not allowed to go to -
The first show was in LA so he took a camera crew down the LA river, into an abandoned Nazi camp, etc.
This week they featured Seattle. Showed the river flume that channels water into the power house to generate electricity, and showed one of the 3 "floating bridges" in Seattle, including going inside some of the watertight compartments.
Pretty interesting show if you like to learn about stuff like this. Terry, though of you watching the Seattle episode - you would be interested in it when it comes up for a re-run.