Only four columns and a corner of entablature survive here, re-erected in the mid-19th century from a jumble of fallen fragments found scattered nearby, pieces that may not even all belong to the same original building. Like Concordia and Juno, it likely had six columns on its short sides and thirteen on the long ones, though so little survives that most of its original appearance can only be guessed at.
Despite that uncertainty, or perhaps because of the elegant, cropped composition the four columns make, this has become the unofficial symbol of the entire Valle dei Templi, the single most reproduced image on postcards, posters, and guidebook covers, arguably more recognisable than the far better-preserved Temple of Concordia.
It's traditionally linked to Castor and Pollux, the Dioscuri, twin sons of Zeus in Greek mythology, though like several temples here the attribution is a later, best-guess label rather than a certainty from antiquity.