This 104-column Corinthian temple in Athens was the the largest temple of ancient Hellas and took 638 years to build.

I saw the Temple of Olympian (Ναός του Ολυμπίου Διός) in Athens when I visited in 2017.
I initially attempted to build it in 2017 but that was a crude attempt and never completed.

Started 17th August. I decided to make it a mortuary temple for Aléxandros III of Macedon, using Trydar's tomb design. Trydar's orders of architecture video was very helpfull so much credit deserved to him.