Sky Citadel is the eight area of Sonic Boom: Rise of Lyric. It is a colossal and marvelous city from the Ancients, located high up in the skies above Bygone Island, held suspended amongst the clouds through mysterious technology. Virtually untouched by time, it is a archeological marvel.
In the quest for the final Chaos Crystal, Team Sonic journeyed to Sky Citadel to find the Sky Crystal. However, they were tricked by Lyric to relinquish their Crystal to him in exchange for Sonic's life. Not beaten though, Team Sonic pursued Lyric through the floating city to stop his plans to destroy the world.