I caught the tail end of a show on TDC, dealing with Leonardo Da Vinci and his achievements. one of his projects was the casting of an enormous bronze statue of a horse-I think it was about 5 times life size. Could 16th century technology have done this? It would require a huge amount of molten bronze-could the furnaces of the day have melted enough metal to do this?
Keep in mind, the statue would not have been cast as one piece. It would have been done in pieces, then assembled.
The bronze horse has in fact been made, twice, by a sculptor with "extensive training in Renaissance art and traditional sculpture techniques."
More info here and here, the latter with a photo of the Milan statue in mid-assembly.