The Small Grave is a small room found at the end of the secret area Inner Wall. The Small Grave has only one item of note in it: a statue of a dead Prinny (The NIS America mascot).
Near the statue there is a sparkle entity, it gives the player the Prinny Cap.
Like all the Areas exclusive to Cave Story 3D, there are files in the game that can be inserted in the freeware port of Cave Story, and be converted to their equivalent forms of the original version. Small Grave would look like this:

Facts[]
- Just outside of the Small Grave is a ghostly, dancing Prinny.
- The Small Grave, Inner Wall and Prinny Cap are all exclusive to Cave Story 3D.
- In the Cemetery background you can see the small grave.
- The Small Grave vaguely resembles the head of a Prinny when viewed on the map.