This is an automated archive made by the Lemmit Bot.
The original was posted on /r/whatisthisthing by /u/NoUsersLefft on 2023-09-06 21:59:09.
This is a pretty uneducated guess but it looks like the tank for what we would call a "long drop" toilet system in Australia. Deployed in national parks or remote wilderness areas, the tank goes in the ground and a toilet sits directly above. They stink horribly as you might imagine.
I'm betting either this or some other form of septic system designed to be buried with the small cylinder on top accessible on the surface.