Based on the girth of the trunk, I think the tree is between 500 and 1000 years old. So it was there in that field during the “Belagerung Wiens”!
It’s a stag’s head oak or stags head oak. Most other oaks consist of a high single trunk but stag’s head oaks spread out after 2 or 3 meters – just like the antlers (Geweih) on a stag. I’ve not seen them outside England but there’s no reason why they shouldn’t grow somewhere else; they’re not a different species. I don’t know why they grow like that and not just straight up.
…says my dear friend Andy!