The Temple of Apollo is being restored slowly and since 1986 has been included on the UNESCO World Cultural Heritage list.
This image shows one side of the temple under the covering tent, which allows light to work by while shielding the temple from
the elements.

The only historical evidence for the architecture of the temple and the date of its construction and dedication to Apollo
comes from the famous early traveler and writer Pausanius in his "Description of Greece" in the 2nd century AD.

The Temple of Apollo at Bassai is a Doric temple, somewhat longer than most Doric temples, but with some Ionic columns on the interior.
It was built between 420-400 BCE This makes it almost contemporary with the Parthenon.
In fact, Pausanius tells us that the architect was Ictinus, one of the two architects of the Parthenon. This has been confirmed by modern investigations.
It is interesting that an architect of this calibre would work in a site so far away from the mainstream and in such a remote place.