Pita Gyros (Thessaloniki) is the northern way to order a gyros in a pita, a regional ordering convention distinct from the Athenian default rather than a different sandwich. The angle here is the swap at the sauce and condiment layer: in Thessaloniki the standard round commonly leans on mustard and ketchup where the southern build leans on tzatziki, and that one shift changes the whole character of the wrap.
The frame is the same as any pita gyros. A warm pita griddled soft and brushed with oil; the carved gyros off the vertical spit; tomato; onion; a handful of fries, patates, rolled into a cone and wrapped in paper. The Thessaloniki ordering reshapes the wet layer: instead of a smear of garlic-yogurt tzatziki binding and cooling the load, the round often gets mustard and ketchup, sometimes with the tzatziki dropped entirely as the baseline. Good execution here still needs something gluing the filling to the bread, so the sauces have to be applied to the pita rather than dribbled on top, and the meat carved juicy because there is no dairy to rescue a dry shave. The result is tangier and sharper than the creamy southern version, with the mustard cutting the fat the way tzatziki would elsewhere. Sloppy work is a thin streak of ketchup and nothing binding, a dry crumbly stack that sheds shavings, or a cold pita that cracks on the roll. The cone still has to seal at the base, and without the body of tzatziki holding the layers it has to be packed tighter.
How it shifts is regional habit, not a fixed recipe, so it pays to say what you want. Some Thessaloniki counters still offer tzatziki on request and others assume the mustard-and-ketchup round unless told otherwise; some build a wetter version, some a leaner, drier one by design. The meat itself, pork or chicken off the spit, is the same animal as anywhere in Greece; what changes is the condiment grammar around it. The Athenian tzatziki-led default and the broader Thessaloniki street-food style each deserve their own article rather than being crowded in here; at this entry the single point is the northern ordering and how a good shop keeps a tzatziki-free wrap from going dry.