The Basilica is the oldest standing temple at Paestum, built around 530 BC, and it looks it. The columns are shorter and fatter than those of the Temple of Neptune next door, and their capitals swell outward with an exaggerated mushroom flare — a feature called entasis, the slight bulge that the Greeks used to counter the optical illusion of concavity in a straight shaft. At Paestum's Basilica, the entasis is pushed as far as it goes anywhere; these columns feel almost organic, like they are straining under the weight above them.
Fifty columns surround the structure — nine across each short end, eighteen along each long side — which gives it an unusually wide double-nave plan inside. The roof is long gone, but the stone grid of the outer colonnade survives. Standing at the corner where the Basilica meets the Temple of Neptune, you can compare the two buildings directly: the visual difference between Archaic and Classical Greek architecture is immediate and striking.