This doorway leads nowhere.

What looks like a Stargate has stood on a rock at the edge of the Aegean for 2500 years and the only reason it is still there is that it was too heavy to steal.

It is called the Portara, and it is all that survives of a temple to Apollo on the Greek island of Naxos.

Around 530 BC, the island's tyrant, Lygdamis, set out to build a sanctuary so vast it would humiliate the Temple of Apollo on Delos, the sacred island where the god was said to have been born.

The marble was cut at a quarry ten kilometres inland and hauled to the shore.

He never finished it, and around 524 BC, a Spartan-led alliance drove him from power, and the work simply stopped.

A Christian church was raised inside the ruins and then, under Venetian rule, the temple was taken apart and carried off, block by block, to build the fortress and the houses of the town.

The doorway was the one thing they could not move. Four blocks of Naxian marble, around twenty tons each, standing almost six metres high.

And if you look closely at the stone, you can still see the bosses: the small raised knobs the builders left so ropes could grip them as the cranes lifted the blocks into place.

They were always chiselled off once a temple was complete. On the Portara, they are still there.

Behold the majestic Portara, the iconic marble gate standing proudly on the islet of Palatia, just off the coast of Naxos town. Bathed in the golden light of sunset, this ancient doorway is all that remains of a grand temple dedicated to Apollo from the 6th century BC!

Temple of Apollo