Avault springs from a(n) which is supported by both a solid wall and four columns.
a.
cornice
c.
keystone
b.
pendentive
d.
springing line

Assuming that you are talking about the cave monasteries of Byzantine Cappadocia, the vault that springs from a Cornice on the west and east walls. While the north side of the Vault is set above an overhang

Start with a good stem and on the top put a kinda wiggly line into a circle connecting to the stem then draw some squiggly lines in the circle that should be about 3-2 inches long