This hidden valley is called Coire Gabhail and is called hidden valley now because it is where the MacDonalds of Glen Coe hid their rustled cattle. There is parking off the A82 that stares directly at the Three Sisters, you’ll head down and to the left, following the clear path and aiming between the two peaks. (This is also the lot for hiking the three sisters) It is a steep and rocky path so it is a hike not a walk! 2.5 miles ~ The sites say 2-3 hours but keep in mind the people who wrote that are in shape and liars so count more like an enjoyable 3-4 hour hike out and back trail.
An hour and a half from Glencoe Scotland there is this gothic revival style castle you can tour and have lunch at. Even some tea if you want! This castle has been the seat of the Dukes of Argyll, chiefs of Clan Campbell, since the 18th century.