Are you aware of any active microwave communication towers [0] that are open to the public?
[0] This means structures whose primary purpose to to act as a communication tower, rather than a tourist attraction (Eiffel Tower) or office building (er, every tall office building ever?).
In the back country, especially in the sierras, you can get pretty close to some microwave and other communication relay stations. Not open to the public, but you can nearly walk right up to them.