The Church of Panagia Chalkeon (the Virgin Mary of the Coppersmiths) lies near the intersection of Egnatia and Aristotle Street, in an area taken up from antiquity by coppersmiths workshops. According to the inscription on the lintel of the west entrance, the church was erected in 1028 on the site of a pagan sanctuary by Christopher, Protospatharios and Catepano (Commander) of Longobardia, his wife Mary and his children Nicephorus, Anna and Katakali. The founder’s tomb is in an arcosolium in the middle of the north wall.

The church is of particular architectural and morphological interest. It is a composite four-column cross-in-square church  with a central dome and two further domes at the ends of the two-storey narthex , and a sanctuary with a three-sided apse to the east. It is built of alternating layers of thin and thick brick (using the so-called recessed brick technique), with the thinner, recessed layers covered in mortar to create alternating red (brick) and white (mortar) surfaces. Morphological features that lend the monument intense plasticity include slender domes, pediments , blind arches, brick half columns, arched ends, and successive openings and conches, all contributing to harmonious spatial composition and carefully balanced proportions. A marble cornice runs around the church; below this on the south side are clay tablets decorated with kufic ornaments to form a frieze . The columns in the church are crowned with tectonic capitals bearing cord-shaped ornaments on the edges, and circular frames with crosses, rosettes and whirls of fire on the sides.

According to an inscription on the intrados of the sanctuary arch that mentions the same sponsor, the greater part of the painted decoration was carried out when the church was first erected. The iconographic programme includes scenes from the Christological cycle in the nave (Nativity, Presentation, Adoration of the Magi, Pentecost), with the Ascension in the dome. The sanctuary has a depiction of the Platytera (Virgin of the Sign), together with full face portraits of prelates and the Communion of the Apostles. The Second Coming is depicted in the narthex.

The original decoration in parts of the north and south walls and on the west side seems to have been replaced in the Paleologan period. All that remains of the paintings are remnants of the Assumption, the Akathist Hymn and some individual saints.

In Ottoman times the church became a mosque, but was restored to Christian worship thereafter. It suffered major earthquake damage in 1933, but was completely restored before World War II. Damage caused by quakes in 1978 led to a new series of restorations from 1980 onwards.