I think that The Colossus at Rhodes was created by piling dirt on the surrounding land as they built up. The Colossus stood 110 feet tall and stood on a fifty foot tall pedestal. This giant of a statue was not standing over the gigantic harbor in Rhodes as depicted in very early art. It would not be structurally stable if that were the case. The Colossus would have to stand near the harbor for it to be close to how it was depicted in art. It fell down in an earthquake but people wrote about "tourists" coming to see the Colossus of Rhodes after it had fallen. The visitors would try to wrap their arms around one of the fingers. This proves that it stood on land but it was probably close to the port. The statue stood 110 ft tall and was made of plated bronze, but how could it be possible if it only had two supports. Well, people probably hid another support like a cloak hanging down to the ground, and since it is metal it would be a strong support. It had an iron frame and was covered in custom made bronze plates. This statue of Helios, which was the titan ruler of the sun and the patron god of Rhodes, was made to last. If the statue was hollow, it would not be structural stable so the people put stone pillars in the supports and filled the rest of The Colossus with rocks to keep it from becoming weak. I believe this theory partly because it is very logical and well thought out with ideas like a hidden third support and filling the colossus with rocks to make it sturdy.
All info from the Unnatural History Museum website, Youtube, and 1001 Documentaries.