The walls are particularly well worth studying, as there are to be found in them specimens of all kinds of building, beginning from prehistoric times. There is even plain evidence that the builders of the age of Pericles were not by any means the best wall builders; for the masonry of the wall called the Wall of Themistocles, which is well preserved in the lowest part of the course along the north slope, is by far the most beautifully finished work of the kind which can anywhere be seen: and it seems to correspond accurately to the lower strata of the foundations on which the Parthenon was built. The builders of Pericles’s time added a couple of layers of stone to raise the site of the temple, and their work contrasts curiously in its roughness with the older platform. Any one who will note the evident admiration of Thucydides for the walls built round the Peiræus by the men of an earlier generation will see good reason for this feeling when they examine these details. The beautiful little temple of Athena Nike, though outside the Propylæa—thrust out as it were on a sort of great bastion high on the right as you enter—must still be called a part, and a very striking part, of the Acropolis. It is only of late years that the site has been cleared of rubbish and modern stonework, and the temple rebuilt from the original materials, thus destroying, no doubt, some precious traces of Turkish occupation which the fastidious historian may regret, but realizing to us a beautiful Greek temple of the Ionic Order in some completeness. The peculiarity of this building, which is perched upon a platform of stone and commands a splendid prospect, is, that its tiny peribolus, or sacred enclosure, was surrounded by a parapet of stone slabs covered with exquisite reliefs of winged Victories, in various attitudes. Some of these slabs are now in the Museum of the Acropolis, and are of great interest—apparently less severe than the school of Phidias, and therefore later in date, but still of the best epoch and of marvellous grace. The position of this temple also is not parallel with the Propylæa, but turned slightly outward, so that the light strikes it at moments when the other building is not illuminated. At the opposite side is a very well preserved chamber, and a fine colonnade at right angles with the gate, which looks like a guard-room. This is the chamber commonly called the Pinacotheca, where Pausanias saw pictures of frescoes by Polygnotus.