In Niccola's day there were many moved by a laudable spirit of emulation, who applied themselves more diligently to sculpture than they had done before, especially in Milan, where many Lombards and Germans were gathered for the building of the Duomo. These were afterwards scattered throughout Italy by the dissensions which arose between the Milanese and the Emperor Frederick. They then began to compete among themselves, both in carving marble and in erecting buildings, and produced works of some amount of excellence. The same thing happened in Florence after the works of Arnolfo and Niccola were seen. The latter, while the little church of the Misericordia on the piazza S. Giovanni was being built after his designs, carved a marble statue of Our Lady with St Domenic and another saint on either side, which may still be seen on the facade of that church. It was also in Niccola's time that the Florentines began to demolish many towers, erected previously in a rude style in order that the people should suffer less by their means in the frequent collisions between the Guelphs and Ghibellines, or for the greater security of the commonweal. One of these, the tower of Guardamorto, situated on the piazza S; Giovanni, presented unusual difficulty to those who wished to destroy it because the walls were so well knit that the stones could not be removed with the pickaxe, and also because the tower was a very high one. Niccola, however, caused a piece to be cut out of one of the sides of the tower and closed the gap with wooden supports, a braccia and a half long, he then set fire to the props, and so soon as these were consumed the tower fell down and was totally destroyed. The idea seemed so ingenious and so well adapted for such emergencies, that it afterwards came into general use, so that whenever it was necessary to destroy a building, the task was speedily accomplished in this most facile manner.