Being a fanboy of Petite Properties dolls house kits, may I present their latest, which might be usable as either a watch tower or a wizards lair:
First two photos are as done by the proprietor, the last is as it arrives. It's a dolls house kit, so you'd need to do a little more work to make it 360 degree proof but it does strike me that it's quite usable as it is, on the edge or corner of a table with scope to show modelling skills inside as well as fighting through the floors.
There's a separate base kit to increase the height, more details here:
https://petitepropertiesltd.com/the-watch-tower.html