Aren't most works-for-hire for by US Government employees immediately released into the public domain? In that case, then, how and why is it that the National

Aren't most works-for-hire for by US Government employees immediately released into the public domain? In that case, then, how and why is it that the National Arboretum is a "copyrighted place"? Also, does anyone know a good primer on copyrighted places in general? My understanding of copyright law is hazy at best, but that seems unreasonable.