Ghibli Experimental Theater On Your Mark (Japanese: ジブリ実験劇場 On Your Mark, Hepburn: Jiburi Jikkengekijō On Yua Māku) is an animated music video created by Studio Ghibli for the song "On Your Mark" (also released in English as "Castles in the Air") by the Japanese rock duo Chage and Aska . The song was released in 1994 as part of the single "Heart". In 1995, Hayao Miyazaki wrote and directed the short film for the song as a side-project after having writer's block with Princess Mononoke. The anime music video is non-linear, providing multiple reiterations and alternate scenes to depict the events. The music video added sound effects to the audio track, but contains no dialogue. Miyazaki purposely misinterpreted the lyrics to present his vision of a world where the surface becomes inhospitable and humans live in an underground city. He made the video cryptic to evoke creative interpretations among viewers.

The music video follows two policemen who raid and massacre a religious cult and find an angelic being, only to have her taken away and confined to a secure laboratory. Haunted by the fate of the angel, the two men formulate a plan and break into the laboratory. Fleeing in an armored truck, the three plummet into an abyss after trying to force past a police aircraft along a narrow, suspended roadway. After a montage of the previous scenes, the armored truck suddenly rockets into an apartment complex, allowing their escape. The three escape to the surface, ignoring the radiation and danger signs, emerging near an encased nuclear reactor. The two men set the angel free and she flies off into the sky.

The music video was well-received and praised for its animation and attention to detail. It premiered as a short before Studio Ghibli's Whisper of the Heart and has since been released on Laserdisc and DVD as part of the All Things Ghibli Special Short Short (Ghibli ga Ippai Special Short Short) compilation.