Point "Opel"

Day 3 in Simmern/Hunsrück:

The large rock on the left at the front door of the land registry office in Simmern shows the original point "Opel" of the European Meridean Arc Measurement in 1870. The little rock in the center is a boundary stone from 1790. The rock on the right seems to be even older than that.
I was very impressed (no one else was).