Perthro's Structures plans to add a variety of new structures that enhance the exploration experience in a way that attempts to not be too invasive. All structures are uncommon/out of your way, or if they are common they are rather small/unimportant. 

Large-Scale Dungeons

These are randomly generated structures that you can find in your world, and are chock-full of treasures and dangers!

GNARLED HALLS

A vast underground system of tunnels made from an ancient hollowed out tree deep underground. The people who originally lived here have long since abandoned it. You can find these in all biomes that are named 'forest.'

STORAGE COMPLEX

An abandoned storage unit situated in the depths of the frozen wastelands. Valuable materials are abundant, but so are mobs. Can be found in snow plains, ice spikes, snowy taigas, snow slopes, and frozen peaks.

Smaller Structures

Random Structures you can find in your world. There are currently 13 of these, and that amount will grow further as time goes on. There are even some structures you can find in the end!

If you dislike any of the structures in the mod or like them to be compatible with modded biomes, I HIGHLY reccomend the use of structurify. This is my first attempt at making a mod and this is an early stage, so all my structures are not final and may be tweaked in updates to come.

CREDITS

• Aureljz: Inspired me to make the storage complex in the first place
• beaniebe: Also inspired me for the same reason. Allowed me to make some of his rooms from his storage complex lethal company mod into minecraft versions for this one. Please check out his storage complex mod, it's pretty awesome.
• Spoons144p: Friend of mine and helped me build some of the larger rooms