Haunted Amusement Park

The Haunted Amusement Park is unlocked by beating Dry Bowser of the seventh mansion and is where Luigi finds the 4th Star Key.

Main Park
The Main Park connects to all the attractions and is where Luigi finds the 4th Star Key. There are no ghosts, but Luigi finds a lone Toad who gives him the key that unlocks the Fun House.

Fun House
The Fun House is where Luigi finds a letter by Mario that says the Shadow Queen has not only created 11 mansions, but has also created duplicates of enemies from his and Luigi's pasts. This is also where Luigi find the Water Elemental Medal. Luigi finds the key that unlocks the Clown Tent.

Ghosts:
Gold Ghosts

Speedy Spirits

Temper Terror

Water Elemental Ghosts

Fun House Terrors

Clown Tent
The Clown Tent is where Luigi finds the Fire Elemental medal and the key that unlocks the House of Mirrors.

Ghosts:
Gold Ghosts

Speedy Spirits

Flashes

Fire Elemental Ghosts

Clown Ghosts

House of Mirrors
The House of Mirrors is where Luigi finds the Ice Elemental Medal and the key that unlocks the Creepy Steeple Tower.

Ghosts:
Gold Ghosts

Ceiling Surprises

Purple Bombers

Purple Punchers

Garbage Can Ghosts

Blue Blazes

Ice Elemental Ghosts

Mirror Terrors

Creepy Steeple Tower
The Creepy Steeple Tower is where Luigi fights Shadow Doopliss and receives the key that unlocks the eigthth mansion. Luigi also receives a token that lets him play the minigame "Freak-in-a-Sheet".

Ghosts:
Gold Ghosts

Ceiling Surprises

Purple Bombers

Purple Punchers

Dark Boos

Garbage Can Ghosts

Blue Blazes

Flashes

Temper Terrors

Ice Elemental Ghosts

Fire Elemental Ghosts

Water Elemental Ghosts

Speedy Spirits

Shadow Doopliss