Haunted House

Greg and Rowley's Haunted House was made by them in the first book and the online version.

Alleys (though nothing got done)

 * Hall of Screams
 * Lake of Blood
 * Bottomless Pit
 * Rat Tunnel
 * Maze of 1,000 Skulls
 * Knife Alley
 * Hand Hall
 * Acid Lake