Between Kusadasi 60 km and Altinkum (Diddim) 20 km.. Not accesible without a car but easy with one. Miletus (Acts 20:17) is the site of one of the most moving episodes in the Apostle Paul's ministry. There is an excellent museum, parking and archeological site. Priene is also close enough to make it worth a combined trip to both sites. A bit of a climb to the Sanctuary at Priene. Cafe and Onyx workshop in the village nearby. Far less crowded and less 'hassle' than Ephesus (though Ephesus should not be missed).
If you own or manage Miletus, register now for free tools to enhance your listing, attract new reviews, and respond to reviewers.