A series of geocaches honoring the intuitive faculty in the human psyche, which can be so valuable in guiding us through life. These caches are placed along a "Bay Area backroad" that is well known to bicyclists, and the best way to find these caches is by bicycle, which will be the most enjoyable and allow you to savor the quest. But if you like, you can also drive to find them, and there is parking quite close to most of them, although for a couple you'll need to walk about 100 yds from the nearest parking.
The "Third Eye" is "a mystical and esoteric concept of a speculative invisible eye which provides perception beyond ordinary sight" so says the Wikipedia article on the Third Eye.