Minecraft hardcore world building ideas?

I play with 3 other people on my survival hardcore world because our last one was destroyed in full netherit and 64dias we live in a village that has big mountains and a canyon only I don't know what else I could build does anyone have any ideas?

You could build a cave system in the mountain which looks rotten but if you do something specific you get into a cave where your camp is and so on.

Watchtowers on the mountains, possibly. An obsavatoriom. Bridges that connect things. An underground system with which you can get up the mountain from the village, etc.