Cache is a small container hidden under natural cover. GZ is within 10 feet of paved walkway, you don't need to go all the way down to the river. Stealth will be required at certain times as arena events draw muggle traffic. Sometimes the area will be blocked off with orange fence due to events on the arena green, if this is the case come back in a few days.
If you are caching after dark, be aware there are rough sleepers in the park and vicinity. The city will try to shoo them away every few months but they come back. There is also a steep drop in the path down to the river.
There is easy access by bicycle or foot from the Guadalupe River Trail. Free parking is available nearby on Autumn Street (except when blocked for arena events). Metered parking is available along St John Street a few blocks away under the Route 87 overpass, just past Henry's. Difficulty is two because of the ground slope and the need for stealth. Please re-hide carefully.
Update 7/17/2017.Cache is replaced but the warnings still apply. Be careful here, the slope may be slippery.
Congratulations to CarlottaP and Oaknest for the FTF!
