The Subway Cave is the largest lava tube you can visit in the Lassen National Forest in Northern California.
Last updated: July 8, 2025
A Complete Guide to Visiting Subway Cave, a Natural Lava Tube in the Lassen National Forest
A lava tube has a magnetizing effect on me. Not particularly crazy about volcanoes, I can’t dismiss nature’s miracle that every lava tube is in essence. My first encounter with this phenomenon was supposed to happen in Arizona. We visited the Grand Canyon State in spring 2021, when a pandemia was still keeping the world pretty much upside down. As a result of this and increased visitation right before the Covid-19, the Lava River Cave was closed.
I was beyond excited when I heard about the Subway Cave in Northern California. Located in Lassen National Forest, about 15 minutes away from Lassen Volcanic National Park, this underground cavern is the largest accessible lava tube in the area.
History in a Nutshell
Some 30,000 years ago, lava began pouring out from cracks in the earth. The molten substance spilled over the floor of Hat Creek Valley, smiting everything on its way.
Eventually the top layer of the ground hardened. But this didn’t stop the lava from flowing underneath the surface. In fact, the hardened crust further stimulated the lava flow, creating a natural insolation from above.
The lava exhausted itself at one point. But the underground tunnels, such as the Subway Cave, still testify to the incredible force of the volcano and nature.
How to Visit Subway Cave
The Subway Cave is the largest lava tube in the lava flow. It spans 1/3 mile and in some areas is nearly 40 feet wide. A few mini tunnels deviate from the main cavern. These are dead-end tunnels, forcing visitors to turn back and follow the main route of the Subway Cave.
Location
The coveted natural landmark in the Lassen National Forest sits off Highway 89. From a small parking lot with two vault toilets, a short hiking trail snakes through the forest to a depression in the ground.
Inside Subway Cave
A few staircases help you get down inside the Subway Cave. Once you make it on the lava tube ground and dive just a few feet farther inside, a complete darkness envelops you. Interpretive signage at the parking lot warns you about it and instructs you to bring along a flashlight or battery operated lantern.
We failed to do it. As I normally stay behind to take pictures, I entered the Subway Cave in complete darkness, all by myself. I could hear voices of my travel companions farther inside the lava tunnel, but couldn’t see anything, not even my own hands.
My phone flashlight was weak against this pitch darkness, only strong enough to illuminate a small area in front of me and save me from falling with my face down on the jagged ground.
I hurried to catch up with the rest of the group. In this spooky and cold place, the last thing I wanted was to face bats living in the lava tube all by myself.
TIP: The Subway Cave has more interpretive signage and maps that show where exactly you are. But even with two phone flashlights, it was hard to see them. So if you want to take the most of your visit to the Subway Cave, be sure to bring a bigger flashlight, a head flashlight, or a battery operated lantern.
Ending the Hike
The 1/3-mile hike ends faster than you expect it. A crack through which the day light penetrates into the cavern means only one thing: the exit. Another set of staircases helps you get out of the lava tunnel.
If you feel like trudging through the dark Subway Cave one more time, turn back and repeat the hike until you get back to where you started. Otherwise, follow the narrow, unpaved trail back to the parking lot.
Things to Know before Visiting Subway Cave
Bring along Flashlight or Battery Operated Lantern
It’s pitch dark inside the Subway Cave. A phone flashlight can help you pass through the lava tube safely, but greatly diminishes your ability to see a lot or take pictures. So, bring along a flashlight. If you forget one, you can rent it at the Old Station Information Center, located 1/4 mile south of the Subway Cave.
Put on a Light Jacket
The temperature inside the lava tube hovers around 46 degrees Fahrenheit. If you are the one who gets cold quickly, pack a light jacket before visiting the Subway Cave.
Beware of Rattlesnakes
Rattlesnakes live in the area along the trail leading to the Subway Cave. Respect wildlife, give the snakes enough space, and don’t bother them if you happen to come across one.
Protect Fragile Environment
The Subway Cave is a unique attraction. The area is free to visit, but needs protection. So, follow the Lassen National Forest’s guidelines. Don’t litter, and keep strictly on the designated trails. No food or water is allowed inside the lava tube. A picnic area is located across the road from the parking lot.
No Pets in Subway Cave
Dogs or other pets are not allowed in the Subway Cave.
The Best Time to Visit Subway Cave
Hiking through the Subway Cave is possible from April through October. Moreover, if you arrive during weekdays or early in the morning like we did you are more likely to have the entire lava tube all to yourself.
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