Mount Diablo, overlooking high above San RamonI drove  is the name sake of the same amateur radio club that organizes Pacificon.  the larges ham convention on the West Coast.  I drove up to this summit with Ted, W6TED after Pacificon and can say, the drive was worth the view.  

The road is paved all the way to the top.  The road is VERY curvey, narrow and has a lot of bikes.  So if you are pulling a trailer, you should leave it at the bottom.  (Watch out for bikes zipping down the hill as well.  Because the summit is  in a State Park, it also counts as a POTA.  

We still had a long drive back to San Diego in front of us so we didn't have time for more than 10 VHF contacts.  This was made difficult by all the RF up there (I should have mounted my filter).

All in all - I highly recommend this summit just for the views and cool history.