Ideas to incentivize exploration

Howdy, I am new to modding but have started working on a project that will add a progressing story as well as a collection of tool and weapon modifications to adjust playstyle. nothing crazy enough to throw off the games balance, but enough so players can set up specific builds to suit how they want to play. As of right now as the player explores they can slowly find bits of the story as well as unlock the recipes for these customizations over time. 

While I think these recipes are a fun addition to the game and I hope the story is compelling I would really like for my mod to get players excited to explore more in hopes of getting even further. The only other thing I can think of so far is have each of the structures that contain my progression items have a few items or blocks in their loot or build that are more difficult to get so players feel like finding the structures is a reward in and of itself. If you have any ideas of an item or block you'd be excited to come across let me know. 

Also if anyone has any ideas or examples of games or mods that incentivize exploration really well I would love to hear it! Thanks!