The Floating Catacombs are an upside down version of the Catacombs in Castlevania: Symphony of the Night. This area has the most drastic changes given to it; lava now appears to be molten snow, snowflakes drift down in some places, rocks appear to have formed into crystals, and the once green bricks are now all a menacing red. The theme music of this area is Curse Zone.
The Floating Catacombs are the highest stage in the game. The only way to reach them is by going through the Cave. This area is optional because there is nothing there that is related to the main story other than fighting some unique enemies and finding more new items.
What also dwells in the Floating Catacombs is one of the game's toughest bosses: Galamoth. His attacks include throwing large shadowy balls and using his rod to electrify the hero. The fastest way to beat him as Alucard is to use the Alucard Shield and the Shield Rod combo to drain his health. Another good strategy is to equip the Beryl Circlet found in the Reverse Entrance; it negates Galamoth's electrical attacks making the whole fight much easier.