I love 'em! They are nothing more nor less than pointers suggesting a few places you might like to go free-climbing in the way many have been doing since the earliest days of Everquest, and for all I know longer than that. GW2 zone architecture isn't as clamberable as, say, Vanguard, but you can get to the top of a lot more things than you might imagine and just knowing it can be done is a great spur to giving it a go.
I did a fair amount of rock-climbing in beta before Vistas turned up because, well, you have to, don't you? What Vistas add is some structure and a nice way to record your climbs. I'm not much of a completist but when I noticed that Black Citadel, the utterly wonderful Charr home city, has just the five I thought "even I can focus long enough to do that". So I did. And here's how.
1. Gladium Canton
Easy as walking into a room. Because it's in a room. Not much of a view, unsurprisingly.
2. Great Imperial Smelter
Bring water. And asbestos soles. As easy as the first one, it's just up some walkways looking down on the biggest forge you ever saw. What are we building in there? I could tell you but then I'd have to...you know the rest.
3. Canton Factorium
4. Ligacus Notos
First one that requires some actual climbing. Just a few hops up a smallish rock. Nice spot for a picnic at the top and a really lovely view of some bits of Ascalon we didn't knock down when we improved it.
5. Ruins of Rin
There you have it. Five easy Vistas to get you started. Get your hobnails on and get clambering!