Telepherique du Saleve
A fun experience in the Alps is literally just a city bus ride away. The Telepherique du Saleve is a cable car that takes you up to the top of the Saleve mountain ridge.
It takes you up 1100m in just a few minutes. When you look at the cable car from a little ways away on the ground, it looks like it goes straight up, so the ride is a lot of fun.
There is a little restaurant at the top, and a nice hiking trail that takes you along the ridgetop. I was there in June and only saw a couple other people while I was hiking. It has a perfect view over the Geneva and Lac Leman area valley from many points along the trail.
There's is also a "parapente" club a little ways up the trail from the cable car stop. That's a type of para-gliding. You can watch the gliders sailing all along the ridge on the updrafts.
Take the #8 bus to the end of the line at Veyrier-Douane. From there, walk across the border, hang a right, and follow the signs for the Telepherique du Saleve. It is just a regular CHF 3 "tout Geneve" bus ticket to get there. They do sell a combination bus and cable-car ticket, which might save you just a couple francs. It's about CHF 17 for the round-trip cable car ride. Or you can only take it one way and hike the other (down I hope!). You can also take your bike along on the cable car for free.
This is a great outing for its proximity to the city, the ease of getting there, and having the fun cable car ride and nice hiking trails at the top.
From journal Fun and Physics in Geneva, Switzerland