Not much is known about the geographical structure of the island, as most of the time spent here is concentrated on Lacrima Castle. What little that is known is that it has a cliff called Wilhelm Bluff, presumably at the very edge of the island. According to Fia, it's a dangerous place.
A sprite species known as the Arcs lived here and kept Lacrima Castle. They apparently lived in densely populated village(s) on the island, as hinted by Serene, the last of her kind. During the visit in Riviera: The Promised Land, all that remains are the demons who have retaken the Castle.