A blue green jewel, Beta Delphini II, home of the turtle like Chelonians. The world is old, and bears many scars, the craters from orbital bombardment and high power explosions, rings of dust and debris that were once starships, habitats, and fighter craft. But the world below remains tranquil, its wounds covered with blue seas and green forests.
In the middle of a desert in an oasis is a single prospering oak tree. Near the tree is a large pool of water. Drinking from the water is said to give you eternal life but really only extends your life for as long as you continue drinking from it. Those that have found it and left, have never found it again. Some search for it still.