http://www.coralcastle.com/ contains pictures of a beautiful coral castle built within 28 years by one man and a few pieces of simple equipment. He claimed to have used the same secret the Egyptians used to build the pyramids, but sadly he took that secret to the grave with him. Anyone care to try figuring this one out?
I believe that, for the towers at least, he moved the earth to a downward slant and shifted a block of coral into the hole, then moved it up from there (reduction of weight). then he refilled the earth back in. As for putting other pieces on top of a pieces, a picture of him using a tripod with pulleys was most likely used to put small pieces on top and to tilt other large objects. Even with that mechanism though, it is hard to picture how he could have moved around much larger objects like the 9-ton gate into an upright position and onto an old truck bearing. Coral is quite dense.
As for the hole in the 9-ton gate, constant erosion (perhaps a dripline leading through the exact center) would do the trick to create an almost perfect round hole from top to bottom. This would probably mean that the gate was one of the last pieces put up.
Any other theories/observations of the different components?