What advantages did the Romans find in using a cross vault instead of a barrel v

Question: What advantages did the Romans find in using a cross vault instead of a barrel vault!?
Best Answer - Chosen by Asker:

A cross vault is two barrel vaults intersecting @90degrees, so one cannot be used without the other!.

However the Romans esp!. in the East, use the feature in localised areas of ceiling (say, the top of a church tower)!. This is something of signature detail of eastern architecture & allows 4 lit gables @ roof level!. Several of these features can be butted together to form a less "tunnel-like" walkway than a pure barrel vault!.

http://en!.wikipedia!.org/wiki/List_of_arc!.!.!.Www@QuestionHome@Com