St John is believed to have spent the last years of his life in Ephesus writing his version of the Gospel. Emperor Justinian (527-565 AD) believed that a tomb dating from the 300s was John's, so he built a great church above it in the 500s.
In later centuries the ruined church was pillaged for building materials, but restoration allows you to see its extent and to imagine its beauties.
Plan to spend about 30 minutes here. You can easily walk here from the center of Selçuk.
Just down the hill from the basilica is the 13th-century İsa Bey Mosque, open for free (it's a working mosque) and worth a look.
St John Basilica is about 3.5 km (2 miles) from the Ephesus archeological site.
In the years 654-655 the Ephesus area was invaded by Arabs. This fortress was built on the top of Ayasoluk Hill to protect St. John's Basilica from further attacks. The fortress consisted of thick walls surrounding the temple as well as a fortified gate and 15 towers. The view from the fortress is incredible as you can look out across the farm lands and the ancient ruins below.