<p>VATICAN CITY - The sense of impenetrability begins at the Vatican gate just beyond St. Peter's Square.</p>
<p>Swiss Guards wearing the colors of the Medici flank the portals of the thick, cappuccino-colored walls and lift their pikes to allow passage only after receiving orders. Farther inside, a gatekeeper checks his list before giving a reluctant nod for a visitor to enter a 12-foot door reinforced with steel and iron spikes to repel invaders. It swings open to allow a visitor into the inner courtyard of the Congregation for the Doctrine of the Faith.</p>