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Lost Sentinels

Colorado > Boulder > Flatirons > North
Warning Access Issue: 2024 Crag Closures & Temporary Trail and Raptor Closures DetailsDrop down


The Lost Sentinels are a couple of obscure 200 foot Flatironettes that sit, hidden, to the East of the Royal Arch trail just South of Sentinel Pass.

The two formations provide fun class 3-4 scrambles. The Southern one has a really cool ridge that provides great exposure on solid rock and moderate soloing difficulty.

These formation run parallel on a East-West direction. The top of the Southernmost formation is crowned by a large pine tree.

Getting There

The easiest way to reach these formations is from the Royal Arch trail. Once past Sentinel Pass, look for a trail post (no sign)on the left a few feet after the steep downclimb from the Pass. This post marks an old, unkept, trail (Woods Quarry trail) that heads down steeply to the East. Descend the trail and after some 200 feet head South until the Lost Sentinels come into view.

Routes from Left to Right

4th 1 2 I 2 M 1b
East face / Lost Sentinels
Route Name Location Star Rating Difficulty Date
East face / Lost Sentinels
4th 1 2 I 2 M 1b Trad

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Southern Lost Sentinel, east face.
[Hide Photo] Southern Lost Sentinel, east face.