You Asked:

How do they manufacture huge granite columns for ornate buildings? — Allen, Greenville, Ohio

Marshall Brain Answers:

For thousands of years, people have been making stone structures by hand. They cut the rocks out of the ground by hand, carved them by hand and then hoisted them into place. This was true of the pyramids 4,000 years ago as well as things like the Parthenon built around 440 BCE.

This is a fascinating video from the NOVA series that shows how the stonemasons of ancient Greece created such an amazing structure by hand:

Today they carve stone in much the same way. Even the National Cathedral in Washington DC, built in the 20th century, was carved almost completely by hand. Modern stonemasons carve the stone with traditional hammer and chisel, but also with power tools like circular saws and power chisels that work like small jackhammers. You can see stonemasons at work in these three videos:

World Skills Championship 2007 – Stonemasonry

There is also some headway being made on machine carving, as demonstrated in this video: