Owing to the great height of Mount Etna, the lava seldom rises so far as to flow from the summit. It more frequently bursts forth from the flanks of the mountain; and in this manner there have been formed numerous smaller cones, of which several have craters of their own. Hence Etna is rather a group of volcanoes than a single cone; but all these subordinate volcanic hills cluster round the flanks of the great central summit. Etna may thus be regarded as a fertile mother of mountains, with all her children around her. Some of these hills, her offspring, are covered with forests and rich vegetation--such having enjoyed a lasting repose. Others are still arid and bare, having been more recently formed. Owing to this peculiarity in its structure, Etna does not present that conical aspect which characterizes most other volcanoes. Strange as it may seem, there are, on the sides of the mountain, caverns which the Sicilians use for storing ice. Some of these caverns are of vast extent. One called Fossa della Palomba measures, at its entrance, 625 feet in circumference, and has a depth of about 78 feet. This great cavity, however, forms merely the vestibule to a series of others, which are perfectly dark. Another striking feature of Mount Etna is the Val del Bove. It is a deep valley, presenting, when viewed from above, somewhat of the appearance of an amphitheatre, It stretches from near the summit down to the upper limit of the wooded region of the mountain, and has a remarkably desolate aspect--presenting a vast expanse of bare and rugged lava. Of the numerous eruptions of Etna, one of the most memorable was that of 1669, when on the flank of the mountain above Nicolosi, about half way between Catania and the top of the great crater, there was formed an immense rent about twelve miles long, from which a vast torrent of lava descended. After flowing for several miles, and destroying a part of Catania in its course, it entered the sea, and formed a small promontory, which has since proved very useful as a breakwater. But besides this stream, there were at the same time thrown up such immense quantities of ashes, cinders, stones, and other matters, that they formed two conical hills, more than three hundred feet in height above the slope of the mountain from which they rose, and measuring nearly two miles in circumference at their base. These hills were named Monti Rossi.