They were perhaps the last of their kind. Tradition has quite incorrectly ascribed them to Albert Durer. Not only were they built thirty years after his death, but they are in principle entirely opposed to the views expounded in his book on the “Fortification of Towns.” This book, which appeared in 1527, broke completely with the old mediæval art of fortification (the theory of which may be said roughly to have consisted in an extensive use of towers), and recommended the construction of such bastions as the Köcherts-zwinger, or that in the neighbourhood of the Laufer Thor (1527) which form the starting-point of modern fortification.
The round towers, however, were not the sole defences of the gates. Outside each one of them was a kind of fence of pointed beams after the manner of a chevaux-de-frise, whilst outside the ditch and close to the bridge stood a barrier, by the side of which was a guard-house. Though it was not till 1598 that all the main gates were fitted with drawbridges, the wooden bridges that served before that could doubtless easily be destroyed in cases of emergency. Double-folding doors and portcullises protected the gateways themselves. Once past there, the enemy was far from being in the town, for the road led through extensive advanced works, presenting, as in the case of the Laufer Thor outwork, a regular place d’armes. Further, the road was so engineered as not to lead in a straight line from the outer main gates to the inner ones, but rather so as to pursue a circuitous course. Thus the enemy in passing through from the one to the other were exposed as long as possible to the shots and projectiles of the defenders, who were stationed all round the walls and towers flanking the advanced tambour. This arrangement may be traced very clearly at the Frauen Thor to-day. The position of the round tower, it will be observed, was an excellent one for commanding the road from the outer to the inner gate.
The entrance and exit of the Pegnitz were two weak spots, calling equally with the gates for special measures of defence. They were completely barred by “Schossgatter” as they were termed—strong oak piles covered with iron—set beneath the arches that spanned the river. Strong iron chains were stretched in front of them, forming a boom to prevent the approach of boats. The tower at the exit of the Pegnitz was erected, we know, in 1422. It is mentioned by sixteenth-century chroniclers as the Schlayerturm, and, though it has lost its former height, it serves to-day in conjunction with the adjoining building over the water as a jail.
The most vulnerable points were thus provided for. The rest of the enceinte consisted of the ditch and walls and towers. There were two lines of walls and towers enclosing a space which in peace-time served as a game-park. Celtes in his poem in praise of Nuremberg boasts of the rich turf growing there, upon which grazed splendid herds of deer. The Tiergärtner Thor, however, did not derive its name from this game-park (Tiergärten), but from another earlier one belonging to the Burggrafs.
The interior line of walls was the first to be built. It was made about three feet thick and twenty-two feet high. Originally there were no buttresses to it (as one may gather from the short length of old wall, north of the Spittler Thor, where the inside of the wall is plain), but afterwards buttresses were added along the whole of it, at a distance of eighteen feet or so from centre to centre. About four feet broad, they projected some two feet beyond the actual wall. They are joined by circular arches, the coins of which are walled up. The blinded galleries thus formed are still frequently used as workshops.
The top of the wall is about three yards broad, thanks to a coping stone which projects on each side. Along the outer edge of the coping stone runs a crenelated wall, only a foot and a half thick. Seeing that it was already at the time of construction exposed to artillery, the thinness of this wall is somewhat surprising. Probably the Nurembergers knew that the neighbouring nobility could not afford a heavy and expensive siege-train. A roof, composed, according to the poet Celtes, of tiles partly glazed, was erected over the crenelated wall and thus formed a covered way. The crenelles were furnished with hanging shutters, which had a hole pierced in them and were adapted therefore either to the fire of small pieces or of arquebuses.