OBK #2 Traditional Geocache

This is a resurrection of an earlier cache of mine. Hopefully I've found a muggle-free, landscaper-free hiding spot. 

When you post, please make a guess identifying the very large structure to the southwest of the cache. Believe me, you can't miss it! You get "extra credit" if you can tell me why the cache is named OBK! If you're right, I'll encrypt the log entry! On windy days it makes an incredible sound! Some days the park will be empty, on others much stealth will be required.