The walls to the north of the temples are perhaps the most impressive part of the excavations. The mound on which the city is built reaches here its greatest elevation, and the gigantic masses of the fortifications rear themselves up from its very base. Time after time the kings of Assyria renewed these bulwarks, setting them forward further and further against the river, which once washed their foundations--its bed runs now a little more to the east, where the stream still flows under the eastern quays of Asshur. The upper parts of the walls are of unburnt brick, but the lower, as Xenophon observed at Nimrûd, are cased in massive stone. The stonework was not in reality as durable as the brick, for the Assyrians had no binding mortar, and the stones, being set together with mud, could not resist a pressure from behind, such as that which was offered by the mound itself. A mortar of asphalt is sometimes used in sun-dried brick, but binding mortar seems to have been a discovery of the age of Nebuchadnezzar, since it is first found in constructions of his time at Babylon. The fortifications sweep round southwards to the Gurgurri Gate, well known in inscriptions, and identified by epigraphic evidence. Between the gate and the temple and palace area, a great part of the ground is covered with a network of streets and houses belonging to a late Assyrian period. The larger houses consist of an outer court with rooms for servants and dependents, roughly floored with big cobblestones and traversed by a pathway of smaller cobbles whereon the masters could cross to the inner paved court round which their chambers lay. Every house, however small, is provided with a bath-room. The whole complex has the appearance of another Pompeii, though it is more ancient than the Italian Pompeii by six or seven hundred years. Down in the plain, outside the city walls, stood a magnificent building which has been christened by the excavators the Festhaus. It is a fine open court, surrounded on two sides by a colonnade, while on the side opposite to the gate there is a raised platform of solid masonry. The court must have had the aspect of a formal garden, for at regular intervals there are holes in the hard conglomerate of the floor which the excavators conjecture to have been filled with earth and planted with shrubs. In this colonnaded garden was celebrated the spring sacrifice, the annual festival in honour of the fruitful earth. The plan of the building is not Assyrian--the column itself is a non-Mesopotamian feature--but whence it was derived it would be impossible as yet to say.