The maintenance console for the computer I used to work on - the NORD SAGE Air Defense computer (Built 1959 - decommissioned circa 1984). (This is not the computer it's just the maintenance console for one of two computers. The actual computers had many thousands of vacuum tubes and took a huge amount of floor space.)
granite rocks - hikers started stacking them up and there are now trails where you have thousand of these “granite jenga towers” marking the trails or filling up open areas.