Mine would have to be Hampton Court Palace.
One day, a few years back, I found myself with nothing to do on my day off, so I decided to drive up to Hampton court palace.
When I got there and was about to pay for a ticket, the lady that was selling the tickets asked me if I wanted one of those portable information listening devices. Normally I wouldn't bother with these - in favour of reading the info, but this time I decided to pay the extra couple of quid and get one. I was glad that I did, because it made the experience a lot more fulfilling.
At one point I was chatting to a couple of the security guards about the ghost that's been reported there. One of the guards said that there is one particular ghost that knocks the guards hats off when they are doing the rounds at night. I was studying his face for any traces of mirth, but he was being serious.
I went to The Tower of London a few weeks after, but left underwhelmed.