The Pendentive Flying Buttress                         -      N      - 
(-------------------------------------------------)     W <---(M)---> E
                                                        -      S      -

The central dome rests on four pendentives, by transferring the weight to
piers, rather than to the wall itself.  This construction method makes
possible a lofty unobstructed interior space.  The arched flying buttress
bound by the two pendentives support the dome by converging from these
massive piers.  A dynamic solution to the problem of setting a round dome
over a square space.  The arcade spills out to your north, south, and east. 
To your west extends a lavish transept, illuminated by a large stained glass
window at the far end.