The small mountain town of Julian, California is well-known regionally for its delicious apple pies, but the historical heart of the place is best found off the main road a little way.
In 1870, gold was discovered in a small seasonal creek and this led to the discovery of the source: a vein of quartz running through the mountainside. Through mining, five veins were eventually discovered and mined in the ensuing gold rush.
The abandoned gold mining system that the original town was built around still exists and a local business offers tours. Walking through the old mine, you can see where they encountered each of the veins and began tunneling in a new direction. All the old gear is there to be seen, and though there is a modern lighting system and some wooden structure for safety, much of the mine is preserved as it was during operation.