HSR Adimus
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This park is pretty awesome. They have a lot you can do here. There's a pump track, skateboard park, playground, baseball field, and hiking trails.
The trails here are great and do have river access if you want to dip your toes.
During the winter people will sled down the hills or build snow sculptures and forts in the fields here.
Heading in to the park is a nice break from the generally busy Leavenworth business area.