One of the highest passes in Europe the Stelvio also has these remarkable spagetti-like roads leading up to it from both sides. I rode up from Bormio, the south/eastern side and can recommend it. The climb starts in the town but with just one sign in the centre to show you the way it can be a nervous first few minutes - am I really on the right road? A sign says "turn 39" and that confirms it - there are that many corners to the top.
Initial climbing is hard, may be 10% + and you seem to be heading into an impassable set of cliff faces. After 5 or more KMs of turns and climbing the road veers right, straightens and flattens to go through a series of tunnels and galleries (tunnels but one side is open. I wasn't looking forward to these fearing that they would be long and unlit. But they turned out to be well lit and pretty short. More gentle climbing comes after them - you can see this road in the picture above coming straight up from the middle right.
More big climbs in the Italian Alps
At what appears to be the head of the valley there is a wall with lot of hairpins making the road go upwards dramatically, and many of these approached 10% at times. After this another long valley opens up towards the right and you again ride up at reasonable pace towards what you can now see is the actual pass top. Right at the end of this valley ride are yet more hairpins to crank you up to the very top, again at 10%.
I'd say it was a very doable pass, no big ramps, and with a 9am start relatively few cars or motorbikes around. The pass top is a traffic jam of fast food, people taking pictures plus gift shops. From here you can look down on the very dramatic North/West approach, this has more roads inspired by spaghetti. Descending them is tough as every corner is an extreme hairpin and this side seems to be much more popular with cars and, unbeliveably, buses in the way. I dropped 15 turns and then rode back up fairly easily, nothing over 10%. Descending back down to Bormio was also a treat, the two long valley roads are open with clear views way ahead so you can descend for several kilometres without touching the brakes.
Top is at 2,758m, you gain 1,560m from Bormio