It is also interesting to see how much steeper the climb is close to the center. Compare the floor along the center wall on the left side of the photo with the outside wall on the right side of the photo. Knowing the slope and the optimal lines to ride in the climb and the descent is undoubtedly a secret to winning the annual unicycle race.
How steep is it, anyway?
The slope and length of the Rundetaarn's spiral ramp is quite different depending on the line you take.
Why It's Interesting
The inside edge of the ramp is roughly 3 times steeper than the outside edge. This is obvious once you notice that you need to go up about 15 or 20 feet with each turn, and that the circumference (i.e. horizontal distance) at the inside wall is about 1/3 the circumference at the outside wall. So maybe a shorter but steeper exercise going up (stay against the inside wall), and a longer and gentler descent to protect the knees (outside wall).
This Gem is sponsored by 130° theft-deterrent security satchels