The Lockheed Martin Solar Astrophysics Laboratory (Lmsal) has been running a small fleet of solar and telescopes for over half a century.
Most of these satellites focus on studying the sun, the space weather caused by it, and the effects of that on our climate. The lab has delivered and maintained some of the most well-known solar telescopes like IRIS and SDO, both of which offer a plethora of solar images that are free to look at for anyone. The group has close ties with NASA and the Stanford University solar physics group.
Like any Lockheed Martin facility the security is strict, but this applies mostly after the lobby. This means that it is possible to see the models and instrumental copies of some of the Lmsal ran satellites without issue.
Most items there are reserve parts of the satellites that got launched and therefore contain real parts. Others are copies to show the size of a satellite. Still, this is heaven for any enthusiast.
Know Before You Go
Do not use their parking lot, come in small groups, and follow the instructions of the guards if they give them. Be sure to inform them you wish to see the lobby display.