Lunia, the Silver Heaven, is the first layer of Mount Celestia, and the closest to the Astral. All portals into the Mount from the Astral, the Outlands, Bytopia, or Arcadia lead to this layer, dumping their travelers in the Silver Sea, a vast endless ocean of holy water that laps at the shores and provides a defense for fiendish forces that may otherwise think to invade. The zoveri are always nearby to rescue travelers, however; none drown in the Sea for want of aid.
The skies of Lunia are a perpetual moonlight night, lit by twinkling, silvery stars. The land is the mountain itself, of course, but it's further surrounded by a number of islands each with their own smaller peaks. On these islands are a number of citadels and villages, each in their own styles and architectures befitting their varied cultures.
As the first layer, Lunia is where one finds the majority of travelers from outside the plane, and in that sense it has the most varied population. Permanent residents, however, include the ubiquitous lantern archons; the lowest ranked petitioners of this plane, floating balls of light seeking to improve themselves and move further up the Mount.