The focaccia di Voltri is the focaccia of a western district of Genoa, and it is defined by being thinner and crisper than the city-center round it is constantly measured against. Where the classic Genovese focaccia is soft, high, and heavy with surface oil, the Voltri version is stretched flatter, baked drier, and pushed toward a brittle, almost cracker-like edge. The dough is still dimpled and still brushed with a salty brine, but it carries less oil pooled on the surface and bakes to a crisp, blistered finish rather than a yielding, glossy one. The contrast with the standard round is the entire identity of the thing, a neighborhood insisting on its own texture a few kilometers from the version everyone else makes.
The thinner, crisper build changes how it works. With less surface oil and a drier, snappier crumb, a voltri shatters at the edge and stays light rather than dense, which makes it a bread eaten for its own crackle as much as for anything on it. As a sandwich base that crispness is a trade. It does not soak up oil and juice the way a soft Genovese round does, so it carries a filling without going slack, but it is also less forgiving: a voltri underbaked loses the brittleness that is its whole point, and one left to sit goes leathery rather than merely soft. It rewards being eaten straight from the oven, warm and plain in cut squares, the salt and the crisp edge doing the work, which is the way a Genoese district eats the bread it bakes through the day.
The named relatives are each a position on the same axis of thickness and oil. The plain Genovese round is the soft, oily reference. The focaccia di Noli sits between them, lean but not as crisp. The unleavened focaccia col formaggio of the same region is the cheese-sealed outlier that shares only the family name. Each is its own subject and deserves its own article rather than being crowded in here.