As you arrive at the harbour you will see the immense marble portal called the Portara, on the islet of Palatia. Joined to the main island by a causeway, it is the ancient entrance to the temple of Apollo, which was begun in the sixth century BC but never finished. It is definitely worth a visit, particularly at sunset.
Naxos harbour is dominated by a conical hill, topped by the ruins of an impressive Venetian Kastro. Around it are multitudes of high, cube-shaped buildings that extend like giant steps down to the seafront.