Watchtower
From up here, it all looks like ours.
Claims land, so other players can’t build on it. It claims 18 tiles around it, more the higher it stands above the land around it (up to 9 extra tiles).
It burns a log every 4 hours, and claims only while lit and connected to its district. Cut off, it goes out and keeps its logs.
While enemy troops or bandits stand on its land, it sends an automation signal: wire it to close a Gatehouse or start a hoarding on its own.