Project Zulu is a minecraft mod that attempts to add flavor to minecraft by adding unique mobs, blocks, and structures to the overworld. For example a new block Nightbloom is added which changes form and glows at night. A common structure found is the labyrinth, showcased below, that contains two types of monsters: Minotaurs and Haunted Armor.
Important
The Official wiki contains specific details on all blocks, structures, and options provided by Project Zulu. The Minecraft Forum Thread is a good place to be kept up to date with the latest version. Also via Blog or Twitter.