Following the Central Cross-Island Highway, at Yanzihkou (Swallow Grotto) the rock cliffs of the Liwu River gorge seem to reach to heaven while the river runs its swiftest and the distance between the gorge walls so narrow that they almost seem to touch each other.

Along the Yanzihkou (Swallow Grotto) trail which runs about a half kilometer starting from the entrance to Swallow Grotto to the Jinheng Bridge, you can enjoy the sights of the Liwu River from nearly straight above the water, the potholes on the cliff faces, the springs sprinkled along the lower parts of the walls, as well as the famous rock formation "Chieftain's profile rock".

As of early 2005 the Yanzihkou (Swallow Grotto) Trail was separated from the highway by a simple concrete divider. The road was narrow, resulting in frequent congestion in the area. Consequently, the Park Administration set about building a two-lane tunnel for vehicular traffic to let walkers enjoy the sights of this spectacular part of the gorge uninterrupted by cars and buses. There are two Swallow Grotto (Yanzihkou) tunnels, linked by Ludan Bridge- were completed in June 1, 2007. West-east vehicular traffic must use the tunnels.The old highway is now a pedestrian path and is also open to vehicular traffic going east only that must proceed slowly.