lots of rounds stacked and carved to get slanted shape.
can adjust size of rounds to get smaller as go nearer top so as less to cut away (of course that means less for cake balls)
top is backed in soup can OR is several small rounds cut using biscuit cutter from a regular single layer and then stacked.
roof could be mini-wonder carved or stack of small rounds carved.
pretzel sticks for uprights of railing and licorice lace for top of railing or could use more pretzels all glued togther w/ royal.
cover in crusting BC and paint stripe or in fondant w/ fondant strip.
added little lighthouse keeper's house as that's how I always envision lighthouses. that could be just a cube of cake w/ graham crackers to make roof.
----------------------for more inspiration: gallery search results