The first Rothomagus, like the Rouen of to-day, was neither a hill city, for then it would have stood upon the Mont Ste. Catherine, nor an island city like ancient Paris, for the Ile St. Croix was too small. It was essentially a river city; and you may see at once the extraordinary natural strength of its position on the outside of the river's curve (see Map A), instead of on the inside which may have seemed more probable at first but would have left the town defenceless. Even to-day you can only get into Rouen, as into a town that has been battered and taken by assault, through the breach in her fortified lines. If you enter by the railway from Paris, from Havre, from Dieppe or from Fécamp, it is by subterranean tunnels only that approach is possible, and up a flight of steps that you make your first acquaintance with a "coin perdu" of the town, a corner without character, without size, without the least promise of the beauty that is hidden further off. Of all those great gates through which the mediæval city welcomed her dukes or sallied out against her enemies, but one is left, the Porte Guillaume Lion close by the quays, at the end of the Rue des Arpents, which is as faded and decrepit as its entrance.
To understand something of the origins of the town, it is far better to come there for the first time by the river, by the highway that has suffered least change since Rouen was a town at all. Yet the river itself is cribbed within far narrower bounds than when the first huts of savage fishermen were stuck upon the reed-beds of the marsh; for the town was first set upon islets that have long ago been absorbed into the mainland, and the waters of the Seine once washed the boatmen's landing stages at a spot that now bounds the Parvis of the Cathedral. Even now the Seine varies in breadth at this point from a hundred and thirty-five to two hundred and fifteen metres, with a depth of five metres on the quays at lowest tide. These tides are felt as far as twenty miles above the town. They vary in height from one metre to as much as three, and a tidal wave is formed that is one of the greatest dangers of the downstream navigation. Coming up from the sea is fairly easy in almost any kind of stout and steady craft, but it is difficult for all but the best steamers to get down without being delayed, and sometimes fairly stopped, by the great tidal wave at Caudebec or Quilleboeuf. Only when the floods reduce their strength are the tides unable to turn the current of the stream; and flood water is not unusual in a country where the rain blows in so often from the Channel.