The Tholos temple of Delphi, c. 580 BCE and originally with 20 columns.
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Original image by Kufoleto. Uploaded by Mark Cartwright, published on 19 June 2013 under the following license: Creative Commons: Attribution-ShareAlike. This license lets others remix, tweak, and build upon your work even for commercial reasons, as long as they credit you and license their new creations under the identical terms.