Emerald Pools

Several hundred miles to the north of Itza is to be found a place of power named the Emerald Pools. The pools take the form of dozens of placid, lost-strewn ponds which glow with an eerie green, inner light. The pools are especially sacred to the Mage-Priests, each of whom makes a pilgrimage to them every century or so. No Lizardmen other than the Slann are allowed to enter the waters of the Emerald Pools, the Saurus, Skinks, and Kroxigor under strict instruction to await their master's return at the pool's edge. The Slann spend many days in the Emerald Pools, the sacred waters replenishing their bodies and perhaps refreshing their ancient souls.

No intruder has ever penetrated the jungles around the Emerald Pools, even during the tumultuous years of the war against the Skaven Clan Pestilens. The only warmbloods that even know of the Pool's existence are the savage human tribeswomen who haunt the jungles of the region, and these hold them in as much reverence as the Slann, bathing in the glowing green waters of life.

Source
pg. 35
 * Warhammer Armies: Lizardmen (7th Edition)