I would say yes, it is a real anchor from the days of sailing ships, maybe large ocean going vessels like cargo, large military, or whaling ships (guessing on my part). Weight was as much of a factor of anchors as the ability to hook into the sea floor. Here is a link to a smaller one dredged from Lake Erie in Canada - http://www.waymarking.com/waymarks/WM2BEZ. Where was this picture taken? That may help narrow down the type of ship that used this anchor.

Must have been a big ship in the old days, the house is at least 25 ft. tall. So that would make the anchor at least 13-15 ft. in length.

Standard 18th century anchor for large sailing ships - probably european

It's a real anchor, but it's not necessarily from olden days. I used to be on an aircraft carrier. It had bigger anchors than this one. All ships have anchors, at least all US ships.