Pretty close to the Byaduk caves are a couple of tumuli or lava blisters. The tumuli look like small piles of rocks and came into existence when the lava pushed to the surface. I guess, they are tiny volcanoes. Apparently, this phenomenon is pretty rare — there are only 3 discovered sites on earth with such lava blisters. Since most of the tumuli are on private ground, they are fenced it and can only be seen from some 100 meters away. So it was not the most impressive sight on the trip, but they are sort of on the way to the south coast.
The road provides also great viewing spots of nearby Mount Napier, for which a 4WD is suggested. Here is Mount Napier from afar on a hot and dry summer day.