I am a very active person and, hence, find it difficult to sit still for too long. That's not to say I don't know how to relax, however.
Some of my hobbies that keep me active include running, biking, golfing, bowling, and snowmobiling. I enjoy running to the point that I run in actual events!
Keeping my mind active is just as important to me as being physically. I do read the occasional book but I find learning German more interesting. In both cases, it allows me to think in a way that is different from my engineering background.
I also enjoy to travel as it gives me an opportunity to see and do new things. Some highlights include being on top - yes THE top - of the Sydney Harbour Bridge, using my German, albeit broken, to get around in Germany, and seeing the non-touristy parts of DC.
When I'm not out and about having fun (code for "when I'm at work") I'm a manufacturing engineer. As such, I develop specifications for machinery and manage the project to build and install said machinery. It challenges me on a daily basis and can be stressful at times but, at the end of the day, I love what I do.