Situated on the summit of Mount Palomar in the Cleveland National Forest in north San Diego County, the Mount Palomar Observatory has been at the forefront of astronomical research for decades and is home to the world’s largest working telescope, the 200-inch Hale Telescope. You can do a self-guided tour of the visitor’s gallery.
Docent-led presentations are available on most days of the year or plan to visit between April and October, when guided tours are offered on Saturdays and Sundays. The facility has a visitors center, an interesting museum, and a gift store and you can pack a picnic to enjoy in the grounds.