The Etna should be climbed with a mountainbike.
The climb is ranked number in Italy and number in the world.
Starting from Riposto,
the Etna ascent is 38.067 km long. Over this distance, you climb 3074 heightmeters.
The average percentage thus is 8.08 %.
The maximum slope is 21%.
If you want to climb the Etna, you can find more information on how to train to climb the Etna here.