McDonald's has opened a franchise just steps away from the gleaming white marble dome of St. Peter's Basilica, giving indigestion to some cardinals and local business owners.

There was no fanfare for the Friday opening of the U.S. fast food giant's new venue behind a subdued exterior on the picturesque Borgo Pio, just outside the spiritual home of the world's 1.2 billion Roman Catholics.

When the plan emerged last year, one of its most strident critics was Cardinal Elio Sgreccia, who said McDonald's fare was far removed from Roman gastronomic traditions and not the healthiest of foods.