The Caspian Sea, Earth’s largest enclosed inland body of water, is vanishing at a pace that has stunned scientists. Even under moderate warming, a decline of 8–10 meters is expected—enough to drain vast stretches of its northern basin and permanently alter the surrounding environment. Bottom: extent of coastal retreat in the northeastern Caspian Sea between 2001 and 2024. An abandoned ship near the Caspian Sea. Agreements on conservation and adaptive infrastructure exist, but implementation lags behind the speed of the sea’s retreat.