Atmosphere of Harmon Tunnel at Pammel State Park — Winterset
✨ AI impression of the vibe — not a photo of the venue. See real photos on Google Maps →

Harmon Tunnel at Pammel State Park

The Harmon Tunnel is Iowa's only auto tunnel — a 150-foot passage hand-dug through a solid limestone ridge in 1858 as a mill-water chute, later widened for cars, where you actually drive your vehicle through the dark heart of the Devil's Backbone. The tunnel is still the primary road into the rest of Pammel State Park, so every visitor passes through it.

The move: Drive slowly through the tunnel together (roll the windows down to feel the cool limestone air and listen to the echo), then hike the Devil's Backbone trail above to look down at the ridge you just drove through — finish with a picnic on the Middle River bluffs at sunset.

Where: 1900 Pammel Park Rd, Winterset, IA 50273

Hours: Mined 2026-06-07 — confirm current hours before you go.

#only-highway-tunnel #limestone-ridge #drive-through-rock #state-park

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Proof: source 1 · source 2 · source 3

Verified 2026-06-07.