The ancient capital seems to be the present village of Palatia - Saraylar since it has been known as "Palatia" because of the building known as "Justinian's Palace", where the officer responsible for the marble production in the quarries in the name of the emperor lived.
Sources:
- Proconnesus, Catholic Encyclopedia, Volume 12 / 1913, https://en.wikisource.org/wiki/Catholic_Encyclopedia_(1913)/Proconnesus