This area occupies north-western of Toba Caldera, it is a road that connects Tongging to Sumbul and Sidikalang (capital of Dairi Regency). There are outcrops of a Toba Caldera wall sequence, beginning with Paleozoic basement rocks which is the ruins of caldera wall (debris) and the caldera wall consist of Middle Toba Tuff (MTT) fragments.
