Casterly Rock is a fortress that is actually a colossal rock beside the Sunset Sea. Some say that the Rock looks like a lion in repose when the sun sets. The base of the Rock has great sea-carved caverns. Hundreds of mineshafts penetrate the lower parts of the Rock, where many veins of red and yellow gold gleam untouched in the stone (even after millennia of mining). The Rock itself has been measured at three times the height of the Wall or the Hightower of Oldtown (so around 2,100 feet tall). The Rock is almost two leagues long from west to east, and riddled throughout with tunnels, dungeons, storerooms, barracks, halls, stables, stairways, courtyards, balconies, and gardens. The Rock even has a godswood with queer, twisted weirwood with tangled roots. The Rock also has a port inside it, complete with docks, wharves, and shipyards; the sea has carved great caves into its western face, natural gates deep and wide enough for cogs to enter. The Lion’s Mouth is the huge natural cavern that forms the main entrance to the Rock. It arches 200 feet high from floor to ceiling. Over the centuries it has been widened and improved upon. Now, twenty horsemen can ride abreast up its broad steps.
