Moai

The Stone face is a recurring Easter egg in the Final Fantasy series, appearing in unexpected locations, usually on World Maps far from important locations, and having little to no function whatsoever. In most cases, they are a reference to the Moai, monolithic human statues from the Polynesian island of Rapa Nui (Easter Island).

Final Fantasy IV
A stone face appears on the Red Moon. This one is an allusion to the infamous face on Mars myth rather than the Moai. A "happy face" crater and rock formation, inspired by the Galle crater of Mars, also appears.

Final Fantasy V
The stone face appears at the bottom of the ocean.

Final Fantasy VII
A stone face appears on a cliff in the Great Glacier, while other stone faces appear in the Chocobo Racing Arena. This is the first time stone faces appear in locations rather than world maps.

Final Fantasy VIII
In PuPu's sidequest, the UFO is sometimes seen abducting a stone face with its light beam. Colored stone faces are involved in the Obel Lake sidequest, though no graphics are shown for these.

Secret of Mana
A stone face appears on the ocean's surface in the northeast corner of the world map, while another one is seen in a mountain range at the south of Southtown. Like in Final Fantasy IV, these appearances are based on the face on Mars rather than the Moai.