The Graveyard is seen in the episode "Slumber Party Panic." Finn and Princess Bubblegum are conducting an experiment to revive deceased Candy People and turn them into young Candy People again. However, the Candy People came alive as zombies, with a craving for sugar. Finn and Princess Bubblegum retreat to the Candy Castle. Later, Starchy was frightened by a Candy Zombie, and he suddenly exploded while delivering a larger corpse shovel to Princess Bubblegum. The Candy Kingdom may no longer use the graveyard, because of Princess Bubblegum's Decorpsinator Serum.
It is possible that this is the same graveyard in which Finn found Princess Beautiful in the episode "To Cut A Woman's Hair."
It is also possible that the same graveyard appears in the game "Rhythm Heroes" in Marceline´s Henchman level.
It might also be the graveyard in "Ghost Princess" where Finn and Jake try to solve the mystery of how Ghost Princess died.
Princess Beautiful's tomb stone