Castlevania 64/Castle Center

Here's a quick list of all the rooms in this stage, for orientation:
 * Ground floor: corridors, metal arena, torture chamber, arena of the seal.
 * Floor 1:	first goddess statue, lift room
 * Floor 2:	fork, second goddess statue, lizard chambers, broken ladder
 * Floor 3a:	chapel, butlers room, cursed lizardman room, nitro room, cracked wall, library and 3rd statue
 * Floor 3b:	armors room, waitresses room, inventions room, smashers room, nitro room
 * Floor 4:	secret room
 * Floor 5:	planetarium

The torture chamber
Hints from the goddess statues:
 * 1. "The high wall can be destroyed using magical nitro."
 * 2. "A slight shock can cause the magical nitro to explode"

"I am human! I am only in this shape because of a curse! You are an adventurer? I will give you some advice. To destroy the wall you need both magical nitro and mandragora. Place them both in front of the wall. The mandragora will detonate the magical nitro in a powerful explosion. Take this key. You will find mandragora in the torture chamber."

Third goddess statue
Hint from the goddess statues:
 * 3. "Magical nitro cannot destroy the wall until the protective seal is removed."

The observatory
"Arrange the three goddesses under their father, the Sun, to release the seal."

Hints from the goddess statues:
 * 1) "Gold is the color of Venus, second child of the Sun."
 * 2) "Red is the color of Mars, fourth child of the Sun."
 * 3) "Blue is the color of Neptune, eigthth child of the Sun."