[hollerith]

There aren't. I'm guessing you live in a country with vast tracts of wilderness like the US or Canada. Germany is not like that.

This archeological site is a pile of rocks that once was a castle. (The rocks are probably mixed with dirt and plant life and might have been completely buried.)

[fumeux_fume]

I don't think the parent comment meant fully formed, intact castles, but rather the ruins of them.