The Braddock Lighthouse had stood on the point for centuries. No one really seems to have a solid answer for how old it was--it predates the actual manor itself.
For most people, it's a rather neat-looking, if unassuming building--a historical artifact, if you're in to that sort of thing. For mutants, of course, it was once the home base to Excalibur, and was thus awesome for those reasons.
The lighthouse's history was older than that, however. Once having been protected by Captain Britian himself, the Lighthouse had links to older, darker times. Thanks to being touched by an otherworldy source, the lighthouse was imbued with an energy that no one on campus could really detect. But surely, that wouldn't become an issue in the future, right?