Vintage German Etching?

I dont know to much about this piece other than its old. I picked this up from as estate sale a while back for 5.00. The piece is about 1 ft x 1ft. The signatures are tough to read, the name appears to be Frank ???
A very colorful piece of a castle on a hill above a town and river. The back of the frame also has some tough writing to understand. Not pictured is a stamp/sticker with that says W.Welker..Heidelberg...Hauptstr.106. I was told this could be of Castle Rotterdamn in Europe. If you have any info regarding this piece please share.