Hole-in-the-Rock was an awesome pit stop! Being over 100 degrees, we weren't exactly feeling a full hike, so we opted for the 20 minute round-trip walk at Hole-in-the-Rock. And oh yeah, 10 of those 20 minutes were spent taking pictures at the top. Also, it costs absolutely nothing!
The view itself is neat for only a short elevation gain. The novelty of the hole wears off quickly, but it only took 5 minutes of walking to get there, so you get what you put in. You'll still want to wear tennis shoes, but nearly all of the elevation gain is from stairs; no off-roading here.
Parking pro-tip: Don't park at the first lot you see. Keep driving until you've basically run into the Rock. There's a small lot at the very base.