The city centre occupies a picturesque site on a salient, perched high on precipitous cliffs that drop into the narrow valleys of the Alzette and Pétrusse rivers, whose confluence is in Luxembourg City. The  deep gorges cut by the rivers are spanned by many bridges and viaducts, including the Adolphe Bridge, the Grand Duchess Charlotte Bridge, and the Passerelle. Although Luxembourg City is not particularly large, its layout is complex, as the city is set on several levels, straddling hills and dropping into the two gorges.