The exterior of the choir, with its four radiating chapels, its jutting cornices supported by modillions and columns with carved capitals, and its mosaic decoration of black and white stones, is the most interesting part of the exterior The rest of the church comprises a narthex surmounted by a tower, three naves and a transept, over which rises another tower.
The dome and narthex are modern additions.
The addition of a narthex before the main front and a vestibule on the northern side brings the whole western arm of the cross to a square on plan.
The top of the narthex forms a wide gallery, communicating with the interior at the triforium level.
At the west end of the nave are two projecting towers, with a narthex-entrance between them.
The western entrance was approached by an ante-church, or narthex (B), itself an aisled church of no mean dimensions, flanked by two towers, rising from a stately flight of steps bearing a large stone cross.
It consists of a vast nave of eleven bays, entered by a narthex, with a transept and short apsidal choir.
The narthex and baptistery belong to an earlier period.
This last was rebuilt and enlarged in 1843-1844, but preserves the three bays of the Saxon church, with its western narthex, on which was superimposed the Norman tower, which presents its rich front to the street.
One of the most important of these is the gum-resin of Narthex asafetida, which grows abundantly in the high and dry plains of Western Afghanistan, especially between Kandahar and Unculti- Herat.