From the Herculaneum Gate nearly to the Stabian Gate, on the south side, ran a bluff, with a sharp descent. Nevertheless, as a gate was needed on the side nearest the sea, the Water Gate, Porta Marina, was placed here; through it a steep road led to the Forum, so steep that it could not have been much used by vehicles; but that may have mattered little to the fishermen bringing their catches to the market. The Stabian Gate lay in a depression at the end of the lava bed and afforded a more convenient means of access to the city; thence a road ran to the harbor on the Sarno, and to Stabiae. At the left another road apparently branched off from this in the direction of Nuceria, which could be reached also from the conveniently located Nocera Gate further east; here also the slope of the hill was less pronounced. Two gates, finally, gave access to the city on the somewhat steeper east and northeast sides, the Sarno Gate, which takes its name, not from the river, but from the modern town of Sarno, and the Nola Gate; it is at least probable that the road passing through the latter led to Nola. A glance at the plan will make it plain that the streets of Pompeii must have been laid out according to a definite system; an arrangement on the whole so regular and symmetrical would scarcely be found in a city that had developed gradually from a small beginning, in which the location of streets had been the result of accident. Two wide streets that cross the city very nearly at right angles give the direction for the other streets running approximately north and south and east and west, Mercury Street with its continuations, and Nola Street. The former probably served as a base line in laying out the city; this we infer from the fact that while it is exceptionally broad, and the Forum lies on it, there is no gate at either end, and it could have been little used for traffic. Nola Street has a gate only at the east end; the west end opens into the Strada Consolare, which follows the line of the city wall and leads to the Herculaneum Gate at the northwest corner. That the other streets must have taken their direction from these two is clearly seen in the case of those in the northwest part of the city; on close examination it will be found that the arrangement of the rest also is in accordance with the same system, a fact which would perhaps be still more obvious if the unexcavated eastern portion of the city were laid bare. In two instances, however, there is a deviation from this system. One is in the quarter near the Forum. For reasons which have not been satisfactorily explained, the Porta Marina was not placed on the prolongation of the street coming from the Sarno Gate, but further north. In order to reach this gate the street, as shown on the plan, makes a bend to the north which is reproduced in the other east and west streets lying south of Nola Street; west of the Forum, again, the streets converge in order to give access to this gate.