Just up the road from Aspen is a day-use area called The Grottos. There isn't much parking or many picnic tables but across the bridge, which traverses the Roaring Fork River, about half a mile down, the path takes you to a maze of smoothly carved rock tunnels. They reminded me of what we could only hear and glimpse in the depths of the rocks of Jasper and Banff (think Maligne Canyon).
My visit to the Grottos was at the end of the day and the sun was almost gone. But the aspens were still bright.