These incredible pictures show Europe's largest active volcano putting on a rare and spectacular 'smoke ring' display.<br /><br />Holidaymakers caught the moment Mount Etna in Sicily, Italy blew rare volcanic vortex rings into the sky.<br /><br />The phenomenon happens when rings made of vapour are generated by the release of rapid gas and comes after the opening of a new circular crater.<br /><br />The circular rings can be seen in the sky above the tourists and volcano at 1pm in the afternoon.<br /><br />Juliet and Richard, from London, were holidaying in Sicily with their two young sons when they witnessed the rings on April 5.
