This is an Amazing Hole in the Wall.

Very nice. These are the Hyakueda Tunnel and the Hyakueda Iron Bridge on JR Kyushu's Hoki Main Line between Miemachi and Bungo-Kiyokawa stations, where it crosses the Okudake River.



I had hoped to find a picture of Aso Boy! going over it, but it seems that service normally terminates at Miyaji in the Aso Caldera, shortly before the line reaches this section.

Edit: But not always!!!