Ephesus ancient site is a wheelchair accessible place but surface has cobble stones and it is uncomfortable and bouncy. The length of the walkable grounds is approximately a mile and a half long. Therefore, the person in the wheelchair cannot roll it independently; he or she will need a companion. It is steep and hilly; it would be difficult for a person in a wheelchair to traverse and to have an access to many sites away from the main street.
There are two entrances to Ephesus which are lower and upper gates. There are wheelchair accessible bathrooms at both entrances. Even if it is not possible to access the interior part of the buildings, you can start from the upper gate to see the great deal and just be patient with the old marble and cobble stone streets. Or you can start from the lower gate which is easier. You can go as far as the beginning part of the climb to get a good idea of the whole city. Lower gate entrance visit offers you to see not the whole city but two main sites such as Celsus Library and The Ephesus Grand Theatre.
According to many people, the best attraction in Ephesus is Terraced Houses. It is all stairs and there is no wheelchair accessibility.