We rose early to drive the two, three hours from Onundarhorn to hike Glymur Falls (3.8 miles, 1,000 ft elevation gain) in the only day forecasted to be sunny on our trip. It meant doubling back the way we came, but fortunately we were booked for two nights in the South.
I was dragging, but optimistic to see the second (?) highest waterfall in Iceland. Even before we got to the trailhead a smaller, charming waterfall demanded a pit stop. This would be a theme on our trip, so lucky! Sweeping swooping green slopes gave way to a waterway on one side.
I drove for part, getting to learn new roundabout conventions first-hand, including a gauntlet of six consecutive one. Nothing like rapid repetition to help you work things out in your brain.
On foot: after some flat, low-brush terrain, past tiny sprawling civilizations of mosi over rock, and Vottahellir cave (full of legends! And a plaque!) we got to an icy stream. The decision to cross at a wider but shallower point turned out well. I was very glad to have bothered to pack hiking poles mid-stream. What was icy cold turned to pins and needles of pain then, and my brain got to tell my legs to keep going, and faster(!) while my legs threatened to stop working from thinking they were on fire, and to give up all function.