I've just published my newest (virtual) cache, Pohick Loop Trail along its namesake trail, part of Fort Belvoir's Accotink Bay Wildlife Refuge.
The area is open to the public during daylight hours, all year long. You do not need to enter the controlled access are of the base to access this extensive trail system.
I've contacted the Fort Belvoir Environmental and Natural Resources Division in hopes of placing other caches along the trails. If they are not receptive to traditional caches, I hope to be able to at least place some BITcaches, in addition to this virtual.