A young American tourist goes on a guided tour of a creepy old European castle. At the end of the tour the guide asks her how she enjoyed it. She admits to being a bit worried about seeing a ghost in some of the dark cobwebby rooms and passages.
"Don't worry" says the guide, "I've never seen a ghost all the time I've been here"
"How long is that?" asks the girl.
"About three hundred years......."