Wikimedia Commons has a picture where the contents of the plate can be discerned. They are there to help you identify landmarks in the vicinity. These sorts of things are called “orientation tables” in several European languages (French, Dutch…). I have also come across the phrase “viewpoint indicator”.
This is a day and 5 years too late, but it seems to be a solar compass with markings as mentioned showing the directions of different landmarks.
Problem is that it also has hours marked on the dial (including nighttime hours). But as it is currently configured couldn't possibly function as a sundial. If it was, the pin would need to be located at least a few inches north of the center of the dial, and this is clearly not the case.
It reminds me of an English Ordnance Survey trig point. They are on similar concrete pillars. The central spike could be used to accurately locate the theodolite as the bar on a UK trig point does. It would be neat to combine the two uses (information and surveying) into one artefact.