Hellion had so much fun with hiding her first cache (GC1EFZ1)that she's been nagging for a week to hide another one (Ever been nagged by a 5 year old for a whole week? I'm terrified of what she's going to be like as a teenager). She didn't much care where, it just had to be someplace she thinks is neat. The Milwaukee Depot fits her criteria; she (and her brother) had to be physically restrained to stop them from wallowing in the waterfall.
The Milwaukee Railroad ended passenger service and gave the depot to the city of Great Falls in the 1950s, however a quick GIS search shows that it has been privately owned since at least 1999. At least one cache has been archived here in the past, so caching on the property didn't seem like a good idea. (The archived listing GCYNX1 has some history of the place, or the same info can be found on a plaque on the East side of the depot)
Right next to the depot though we have Sight and Sound park (at least according to the sign, but it is called Specimen Park according to GIS.MT.GOV--hence the name of the cache) an isolated city owned park with a few shade trees, picnic tables, parking right on river road, and no cache in it...until now.
Once you log the cache, check out the Milwaukee Depot's sitting area and waterfall (even during the winter--it is integrated into the building's nifty new climate control system, so it flows year round). Although it is private property, the public is welcome to enjoy the area--there used to be a sign saying so, but I didn't see it the last couple of times I was there. Possible Spoiler: It is available during our normal winter, but not when there is a lot of snow..