This stone construction is called Knuten, which means "the knot". It is Norway's first ascending loop road, and it looks exactly as it did when it was built in 1882.
The problem back then was simple: horses and carts could not handle steep inclines. So the road builders created a 270-degree loop where the road curves all the way around and passes over itself. You go under a stone bridge, continue around the loop, and then cross over the same bridge you just passed beneath. A clever solution for its time.
Knuten was part of the original Geirangervegen, built between 1881 and 1889. Before that road existed, Geiranger had no road connection at all. The only way in or out was by boat on the fjord or on foot over the mountains. The whole road was considered such a technical achievement that it received a gold medal at the World Exhibition in Paris in 1900.
Today cars use the newer road which was blasted through the rock just a few metres away. But Knuten was preserved as a monument to the road pioneers who built it. You can walk or cycle on it, but cars are not allowed on the old section.