I just recently started the Basic Run Plus, and there's a difference in the terrain when I run and when I bike.

This might be hard to describe. When you leave the starting circle, if you turn left on the path before you get to the green by the waterfall, there's an archway through the rocks that leads up to the cabins by the windmills.

When I'm running, there's a bridge over the path that the cat-guide leads me onto. We run out, around the moles, and back over the bridge. It looks like a fallen log covered in moss.

When I'm cycling, the bridge/log is not there.

There doesn't appear to be a way to get up onto the ledge when you're cycling, except to bike to the left of the entrance to the tunnel leading up the metal ramp, and from there out to the end of the ledge. Someone posted a map that showed a route for cycling onto that ledge from below, presumably using this disappearing bridge.

I spent about 15 minutes of cycling time bashing myself on the rocks, trying over and over to see if I could make the jump from the top of one of the rocks on the lower side of the path up to the ledge. I never did succeed.

So: does the bridge appear on any one else's cycling? Or does it only appear when you run?

It is only there when you run. I wish I could make that jump too, but my Mii is so bruised and bandaged now that I gave it up and have reserved myself to doubling back on the ledge. I don't jump down because it is longer and if you turn tight you can save time.