This cache is placed near the "stage" off 2nd Street SE. Not many people in Cedar Rapids even know there is a stage down here. Yep, you went right past it on your way to this cache location. It's the LEGO block looking retaining wall thingy.
I'm pretty sure the original plan for this was not to be a stage, but with the flood control structure leaving all the green space between the stage and the river, it led to the idea for an outdoor concert area that is able to hold up to 10,000 attendees.
This stage is the home to the Newbo Evolve Concert Venue events held this summer. You can read more about the event here: https://www.gocedarrapids.com/newboevolve/