From a previous post:

Only somewhat related-- you can drive up to the Keck Observatory on Mauna Kea. You need an offroad vehicle, and you have to stop at least once to adjust to the pressure.

I did it once. Driving to an elevation of two miles is terrifying-- and it is cold (I didn't pack a heavy jacket to go to Hawaii), but the view was unbelievable, and it was great to visit the site of so many PBS specials.

The telescope is operated from the University at the base of the mountain so when you arrive there are a reception area and a sort of a cage in the telescope apparatus you can view the telescope from.

I could dig up pictures if anyone is interested but there are more professional ones online I'm sure.

The Stanford Linear Accelerator does tours from time to time, if you're interested in that sort of thing but don't want to fly out to Switzerland.