Black Moon

The Black Moon is the "egg" of Lilith, a transport vessel created by the First Ancestral Race to send Lilith to Earth. It collided violently into Earth four billion years ago in the event dubbed "First Impact", and came to rest deep beneath the Earth's surface in the region that would eventually become Hakone, Japan. Buried under the surface, the Black Moon formed a spherical underground cavity of gigantic size termed a "GeoFront", around which Tokyo-3 and Nerv Headquarters were eventually built. According to production sketches, the Black Moon is 13.75 km in diameter. It is destroyed in Episode 26'.