Shamballah Lighthouse

Home to devout followers of the Fey of healing and light, this lighthouse is part of a larger city that enters a pocket dimension when submerged under the water. Only those blessed by the Fey's light can enter. Members of the lighthouse are gifted with amulets that allow for entrance into the city. When they stand on the nearby shore, hold onto the amulet, and say the words, "Almighty Lucidia, Light the path." After these words are said, a whirlpool opens in the water, from which the lighthouse emerges. A bridge of light stretches towards you, and disappears behind you as you walk towards the lighthouse. Once you are inside the lighthouse, it submerges and enters the pocket dimension. 
  From within the pocket dimension, the city is lit by a singular star, which is directly above the city. The city appears to be in the middle of space. Celestial bodies move in the sky to signal different things.