Another photo site had this challenge: walk 10 minutes from your starting point in any direction, stop, shoot for 10 minutes, leave and return to starting spot....
Ten minutes in the direction I chose got me to Salem's Riverside Park (good choice of direction on my part, I figured). First time I've been there. The hardest part was staying where I was, taking the stop part literally, and shooting for (only) 10 minutes. Including changing lens, 10 minutes went very quickly. This is a cropped shot, a ramp leading down to a pier in the water.
A good challenge to set yourself. Focusses the mind, doesn't it? Its a good result. One of my favourites in this vein is to take 100 shots in 30 minutes!