The drum seen from the north Bas-relief with Adam and Eve
The main building at Gandzasar, the church dedicated to St. Hovhannes Mkrtitch (St. John the Baptist) (1216-1238), has a rectangular exterior plan and is cruciform inside, with two-storey chambers in the four corners. Like many other Armenian buildings of the 10th-14th centuries, this church too has been wrongly defined as a domed cruciform church or domed-hall. This
traditional type of Armenian monastic church was first built in the 10th century and flourished widely in the 13th.
In the latter century, apart from Gandzasar, there were a series of churches constructed with the same rectangular-cruciform ground plan and four corner chambers in the monasteries of Geghard, Amaghu Noravank', Hovhannavank', Saghmosavank', Haridchavank', Khorakert and many others. The main church of Dadivank', also in the great religious and cultural centre of the domain of Khatchen, was of the same type and from the same century.
The Gandzasar church is not very large: the exterior measures 11.8 by 17.4 metres. The ratio of 1:1.48 between width and length makes the building longer than similar 13th century churches. This is due to the shorter inner lengths of the north and south arms.
The dome is exactly in the centre of the building, so the west arm is long and the chambers long and narrow. The chambers to the east are illuminated by the windows that open on the east facade. The entrance to the groundfloor chambers is from the hall, while the entrance to those on the firstfloor is from the bema by means of a stairway with stone parapet. The rooms to the west get their light from windows opening on the north and south sides of the church; access to them is from the west arm and the first floor is reached by means of stairs with a stone parapet and stalactite decorations.