In the cave system have lots of room: monster rooms, treasure rooms and maybe it will leading you to other dungeons. Continue digging you will find : iron ingot, some gunpowder, bread and some wheat.
In this seed have an abandoned mineshaft. It can be found at the end of the cave system. The abandoned mineshaft have lot of surface ore.
Moreover some extreme hill with larger overhang and jungle can be found close the beach.