Tom Thumb Tunnel

Tom Thumb Tunnel · PinnedAtlas

Overview

What to expect

An opening into an underground passage. Beyond the entrance it is completely dark, cooler, and can be disorienting. Depth and difficulty range from a short walk-in to serious technical caving. Plan for a genuine outdoor outing to reach it.

Location

Where it is

43.44752, -113.49764

Field notes

Plan your visit

Best time to go

Year-round (stable temps)

Caves hold a near-constant cool temperature all year. Watch for seasonal closures that protect hibernating bats, and avoid entry after heavy rain when passages can flood.

Effort

Strenuous

A demanding outing — long miles, steep grades, scrambling, or route-finding. Come fit, start early, and carry navigation and extra water.

What to bring

Plenty of water
Sturdy, closed-toe footwear
Offline map or downloaded directions (signal is often weak)
Tell someone your plan and expected return time
Three independent light sources
Helmet and a warm layer
Confirm the entrance is open (bat/season closures)
Navigation (GPS + backup)
First-aid basics and extra daylight
Appropriate technical gear

Good to know

Access status is unclear. Verify you have a legal right to be here before you go.
Community-sourced from open map data — confirm the specifics before relying on them.
Cell coverage is often unreliable here — download everything you need in advance.
Conditions change fast in the outdoors. Check the latest reports below before heading out.

General guidance based on feature type and difficulty — always verify current conditions.

Stay safe

Safety

Natural areas are hazardous and conditions change fast. Verify access and current conditions before you go, respect private property and closures, and leave no trace. You are responsible for your own safety.

Total darkness and complex passages make disorientation easy — never go alone.
Loose rock, drops, and low ceilings cause most cave injuries.
Caves are cold; hypothermia is a real risk even in summer.
Flooding can occur fast after rain — check the forecast.
The route itself is a hazard — exposure, length, and terrain demand experience and the right gear.

Cave environments are dangerous: unstable rock, drops, disorientation, and hypothermia. Never enter alone, bring 3 light sources, and check access rules — many caves are gated or seasonally closed for bat conservation.

Access unclear — verify before visiting

Explore

Nearby spots

Source: OpenStreetMap contributorsUpdated 19d ago

Community

Latest conditions

No reports yet — be the first to share current conditions.