Greek Doric Order
The earliest Greek temples were built of wood, but as soon as the Greek began to build in stone, about 510 BC, they built in the Doric style. Doric temples are simple and strong, not fancy like Ionic or Corinthian temples.
In Doric temples, the columns have no base, but just sit right on the floor. At the top of the columns, there's a capital made of a sort of small pillow in stone, and then a square block, under the architrave. On the architrave, there are triglyphs and metopes.
In the Archaic period, practically every Greek city-state built its own Doric temples, not only in Greece but also in Greek settlements in southern Italy, Sicily, and Ionia (modern Turkey).
Doric temple at Paestum, Italy
Bibliography and further reading about Greek architectural orders:
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 Might be a bit out of date.