The ruins of ancient Andriake are strewn over a wide area of an approach road to Çayağzı beach, 10km southwest of Demre. The entire site, which sprawls along the edge of a great flood plain, has recently been the subject of large investment and there are good information boards and well-constructed stone paths. Unfortunately the famous granary built by Hadrian in AD 139 has been reconstructed insensitively with a modern roof, and it's difficult to imagine the original building.
In 2009, the ruins of the first synagogue found in ancient Lycia were uncovered here. The new on-site Museum of Lycian Civilizations has good displays. Platforms and hides overlooking the river delta offer fine birding.
Çayağzı's final claim to fame is as one possible disembarkation (or embarkation) point of the famous blue yacht voyages. Dolmuşes run sporadically out to Çayağzı from Demre; your best bet is probably a taxi (₺25).