Japanese Tunnel actually seems to be on the edge of the Davao city. Once you start hitting some of the more hilly area west of the city proper, you'll be coming close to the Japanese Tunnel.
“The area boasts of various restaurants and coffee shops in Davao City. Try places like Tiny Kitchen or Harana Restaurant for sumptuous meals. ”
“Sprawling city park with a visitor center, a collection of native plants & colorful sculptures.”