Minecraft Seed: automix
This seed has a plane land and hills. Zzz, I know, but also it has interesting features. Spawn and see a group of pigs, turn around and see a npc village. Go this way, and you will find some cave entrances on the way. Also, there’s a montain to the left whith some other cave entrances. The 2 caves may be 1 masive one. Who knows there may be a dungeon or an abandoned mine. The only way to find out is to spawn in and have fun.