During two visits I took many pictures of the outside, the second in more detail also.
The chapel that can now be visited as a museum was a burial chapel, a parekklesion (a side chapel) that was added to the south side of the original church (now a mosque) in the early Palaiologan period, and dedicated to Christos ho Logos (Greek: Christ the Word). The small shrine was erected by Martha Glabas in memory of her late husband, the protostrator Michael Doukas Glabas Tarchaneiotes, a general of Andronikos II Palaiologos, shortly after the year 1310.