Castlevania: Order of Ecclesia/Skeleton Cave

As the name implies, this area is full of many skeletons of various types. Skeleton Frisky and Skeleton Hero's attacks are easy to avoid by crouching. White Dragon and Skeleton Rex may pose some problems, but you can level up repeatedly by killing the large number of Skeleton Friskys. Eventually, you will get to an area with a lot of Bone Pillars. At the end of the platform, you can break it to reveal hidden Black Drops. There is a save room just before the boss room.

Boss: Maneater
Maneater is a giant floating skull with three tentacles. It attacks by dropping to the ground, shooting wave projectiles from its tentacles, and dropping bouncing skeleton bones. It is weak to slashing, fire, and light attacks.

After defeating Maneater go to the next room, pick up the Ordinary Rock relic in the chest, and free the villager, George. With the new relic, you can now double jump.