You know the rules; find an historical light house, any where in the world, get a photo with you and your GPS, give us a bit of a run down on it's history.
For example the above mentioned co-ordinates will take you to the Williamstown, Lighthouse and Timeball Tower, which was erected in 1852, and replaced earlier navigational aids established from the time of first settlement in 1835. The time ball apparatus on top of the tower opperated regularly unitl 1926. The ball was raised to the top of the mast and was dropped at exactly 13:00 hours each days and allowed shipmasters to correct their chronometers.
Of course all the usual rules apply, one report per location, per cacher, etc. ect.