November 24th, on the very familiar walk near the main library to the Tucson Museum of Art (where I volunteer as the museum's event photographer... if you'd like to see photos of one especially fun evening, click there), I passed through the western end of Jácome Plaza.
If you've walked through the Pima County Courthouse (with its bright dome), you've probably seen this pocket park. (If you haven't, here's a satellite view from Google Maps.)
The most fun part for me is the set of “viewers” — for instance, the one in the first photo that shows the same scene through various lenses. (You can click on the photo for a larger view.)
Here's a photo of this part of the plaza:
The page About Joel D. Valdez Main Library - Jácome Plaza has much more information, including the history of Jácome’s Department Stores. (You can even book the plaza for special events.)
Location: Downtown, just west of the main library: on Church, half a block north of Pennington.
Hours: You can walk through anytime, though the plaza may technically be “closed”... there may also be homeless folks camped out on benches, etc. Daytime is probably most fun, anyway, because there's more to see with the viewers.