The IsaBey Mosque was constructed in 1375 and is one of the oldest and most impressive works of architecture remaining from the Anatolian times. It sits at the foot of the Ayasuluk Hill between the Saint-Jean Church and the remains of the Temple of Artemis.
The mosque is open for visitors, except during prayer time. There are two main entrances, to the east and to the west. There are inscriptions and shapes present on the western wall. There is also a brick minaret, although the upper balcony of this is ruined. The second minaret is completely ruined.