The well which supplied the second plateau with water, the "Deep Well," _Tiefer Brunnen_, as it is called, stands in the centre, surrounded by a wall. It is 335 feet deep, hewn out of the solid rock, and is said to have been wrought by the hands of prisoners, and to have been the labour of thirty years. So much we can easily believe as we lean over and count the six seconds that elapse between the time when an object is dropped from the top to the time when it strikes the water beneath. Passages lead from the water's edge to the Rathaus, by which prisoners came formerly to draw water, and to St. John's Churchyard and other points outside the town. The system of underground passages here and in the Castle was an important part of the defences, affording as it did a means of communication with the outer world and as a last extremity, in the case of a siege, a means of escape.[25] Meanwhile, leaving the Deep Well and passing some insignificant modern dwellings (_r_), and leaving beneath us on the left the Himmelsthor, let us approach the summit of the rock and the buildings of the Kaiserburg itself. As we advance to the gateway with the intention of ringing the bell for the castellan, we notice on the left the Double Chapel, attached to the Heidenthurm (Heathen Tower, see page 3), the lower part of which is encrusted with what were once supposed to be Pagan images. The Tower protrudes beyond the face of the third plateau, and its prominence may indicate the width of a trench, now filled in, which was once dug outside the enclosing wall of the summit of the rock. The whole of the south side of this plateau is taken up by the _Palas_ (the vast hall, two stories high, which, though it has been repeatedly rebuilt, may in its original structure be traced back as far as the twelfth century), and the _Kemnate_ or dwelling-rooms which seem to have been without any means of defence. This plateau, like the second, is supplied with a well. But the first object that strikes the eye on entering the court-yard is the ruined lime-tree, the branches of which once spread their broad and verdant shelter over the whole extent of the quadrangle. The Empress Kunigunde planted it, says the legend, some seven hundred years ago. For once, when King Henry was a-hunting, he came in the pursuit of a deer to the edge of a steep precipice, and this in the heat of the chase he did not perceive, but would have fallen headlong had not a lime-branch, at which he grasped in his extremity, stopped and saved him. And he, recognising the special protection of the Most High, broke off a twig of the lime-tree in remembrance of his wonderful preservation, and brought it to his anxious wife, who planted it at once with her own hands in the earth, and it soon grew into a beautiful tree.