Large-scale facets, induced by annealing p-aminobenzoate on a Cu{110} surface, are observed in STM. The bunching of {110} steps aligned along the < 112 > directions with a separation of 12.75 Angstrom forms the {11 13 1} facets. STM images show that there are two rows of molecules on each {110} terrace of the facet. The faceting mechanism and the relationship to the adsorbate structure are discussed. This large-scale modification of the surface morphology confirms that the adsorption of organic molecules on metal surfaces may cause a significant amount of mass transport in the process of two-dimensional adsorbate crystallization.