The Monastery of St. Aberkios is situated on the seashore a short distance east of the village of Elegmi (modern Kurşunlu) on the Bithynian coast on the Propontis (the Sea of Marmara). It is possibly identified with the Monastery of the Theotokos of Elegmi, which was restored by Nikephoros Mystikos under Manuel I. Its typikon, dating to 1162, is preserved in the Monastery of St. John the Theologian in Patmos.
It is nearly complete except for the loss of its central dome. This is a single-nave building which was covered with a dome 5 meters in diameter carried on pendentives. The north and south tympana are each pierced by three windows. The apse has a triple window divided by mullions capped with large impost blocks. The latter are decorated on the outside with crosses resting on globes and are certainly of much earlier date than the church. The semidome of the apse is curiously constructed of brick laid in both pitched and horizontal courses. The bema communicates with the prothesis and diakonikon which project on the exterior and are both covered by elliptical melon domes divided each into eight segments. The narthex has a single cross-groined vault that is out of alignment. It may be later than the main structure, although the two exhibit practically the same form of masonry. Various carved elements are scattered about the interior of the church: some of these appear to be of sixth-century date (such as Ionic impost capital decorated with confronted eagles), while others are much later. 
The entire interior of the church was once covered with frescoes of which considerable remains could still to be seen in the 20th century. The frescoes were post-Byzantine, probably of the seventeenth or eighteenth century. There can be little doubt that the church itself is of the Komnenian period. This is indicated, first of all, by the character of the brickwork which is of the recessed course type, the use of which is limited to the eleventh and twelfth centuries. Single courses of brick alternate with single courses of stone, but at intervals there are three or more successive courses of brick. This type of construction was used in the Pantokrator Monastery in Constantinople.