"Horizon" explores Earth's diverse ecosystems, beginning in the ocean, showcasing marine life, and moving through the mangroves with scenes of pelicans and flamingos to emphasize conservation efforts. It transitions to the desert, highlighting reintroduction projects for species like gazelles and ostriches, then ascends into the mountains to document vultures, ibex, and the Arabian leopard. The film concludes with coral reef preservation efforts using 3D scanning technology at King Abdullah University, underscoring the importance of protecting interconnected habitats.