Fluted columns
Most Greek and Roman columns (but not all) were fluted - that means they had narrow channels running up and down them.
Fluted columns from the Forum in Rome
The Greeks probably started this idea because their earliest columns were made out of wooden tree trunks, and when the builders shaved the bark off the trunks it left these vertical gouges. When they began to build stone temples, they copied the gouges from the wood because it made the columns look skinnier and taller and more elegant.
Fluting the columns also gave them more of a feeling of rhythm, which architects working in ancient Greece thought was an important aspect of a temple.
Doric columns usually had 20 flutes, while Ionic columns usually had 24 flutes.To find out more about Greek architectural orders, check out these books on Amazon.com or in your library:
Ancient Greek Architects at Work, by J. J. Coulton (1982). An interesting look at how Greek architects worked.
Greek Architecture, by A. W. Lawrence, R. A. Tomlinson (5th edition 1996). Might be a bit out of date.
