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As you can see from the pictures above, the Doric capital essentially is split into two simple sections. In contrast, the Ionic capital is decorated with large volute scrolls and the ornate Corinthian capital is decorated with acanthus leaves and scrolls. If you want to see some other examples of these capitals (and some other awesome capitals in general), click here and here.
Throughout history, the Greek architectural style has been adopted and revived by many other cultures. The Romans quickly adopted the Greek architectural style (really, they borrowed tons of their artistic ideas from the Greeks), and the term "Classical style" can refer to either Greek or Roman art. However, Romans put a twist to Greek design by sometimes using a superimposed order on buildings which had more than one story - each of the successive stories are decorated with a different order (this is a deviation from the Greeks, who consistently would use one order throughout a whole building). For example, you can see a superimposed order on the outside of the Colosseum (Rome, 70-80 AD). The Doric order is on the bottom level, the Ionic is on the middle level, and the Corinthian is on the top:
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(Note: the fourth level of the Colosseum also is decorated with Corinthian capitals - but these capitals are atop pilasters instead of columns).
Note the large Ionic columns that decorate the porch
Thomas Jefferson, Monticello, Charlottesville, Virginia (1770-1806)
Jefferson used Doric columns for the porch of his home
Jacques-Germain Soufflot, the Panthéon (Ste.-Geneviève),
Paris, 1755-1792
See the large Corinthian columns?
Pergola, Historic Pioneer Square, Seattle (first built 1909)
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Jefferson used Doric columns for the porch of his home
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Paris, 1755-1792
See the large Corinthian columns?
So, where have you most recently seen some columns with Doric, Ionic, or Corinthian capitals? I most recently saw Corinthian columns on this iron pergola:
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