Храм Аполлона должен был стоять в Дидиме и мыслился как нечто грандиозное , во много раз превосходящее величественный храм Зевса в Олимпии. По длине святилище Аполлона достигало 108 метров, а по ширине — 50, в то время как главный храм Греции, храм Зевса, имел в длину лишь 64 метра. У храма Зевса было только 34 колонны, а у храма в Дидиме — 120, причем диаметр их составлял 2,3 метра, а высота равнялась 20 метрам. По расчетам нынешних археологов, одну такую колонну тогдашние строители могли сделать лишь за год.
The fourth largest sanctuary in the Greek world after the Temple of Artemis (and the Heraion of Samos and the Olympieion at Sicily), the Didymaion was built to rival the Artemision, employing one of the same architects, who was completing his work there, and having the same approximate dimensions.
In 334 BC, Alexander the Great liberated the cities of Ionia. Although the oracle pronounced him to be the son of Zeus in 331 BC, it probably was not until about 300 BC (the cult statue of Apollo had been returned in 301 BC) that the citizens of Miletus were able to begin rebuilding the earlier archaic temple that had been plundered (including treasures that had been dedicated by Croesus) and burned by the Persians in 494 BC. Betrayed by the Branchidae, the priestly caste who were guardians of the site, in exchange for their lives, their descendants later were said to have been massacred by a vengeful Alexander. But the project proved too ambitious and the magnificent structure never was completed. One hundred and twenty columns were planned, each over sixty-four feet high (the tallest of any Greek temple). Inscribed accounts of the construction indicate that each column cost approximately forty-thousand drachmas, at a time when a worker earned about two drachmas a day.