1. Monument puzzles[]
These puzzles work off of a newly implemented electricity system. You need to deliver power to a locked door and then use the corresponding key for said door. You can tell that a door has power when the keypad is lit down. Next to the fuse box, there is usually (but not always) a switch you need to activate in order to deliver power. Note that the fuse will deplete even if the switch is not activated.
2. Loot[]
Not much is known about the loot yet although we do know it will respawn every 30 minutes and is different from monument to monument.
3. Door Types[]
There are three types of doors. Red doors, blue doors and green doors. Each of these doors requires the respective coloured keycards to open The difficulty of the doors goes in order of green, blue, red, green being the easiest and red being the hardest. Note that there may be a blue door behind a green one for example, so make sure to have all you need before opening the first one, for the loot can be sparse before the last door in these cases.
Green cards can be found as a drop from scientists, and at the lighthouse, super market and Oxum's Gas Station. Blue cards can be found in vending machines at the Outpost or in loot rooms opened by the green card that do not contain a blue door. Red cards can only be found in crates and behind the locked blue doors. All these cards have a swipe limit, however using them on the wrong door or one that is not powered will not deplete them, but using them on an already opened door will.
Guide Video[]
Rust Beginner's Guide - Where to find all Keycards
Here's a video telling you where to find all the keycards in Rust.