With the Geneva transport card you can get easily and for free to the cable car.
Simply take the bus to Veyrier-Douane.
From there, it's about 0,5 kilometer to the cable car entrance.
Prices are reasonable (adult: 10 euro for a return ticket).
The view is amazing: you can see lake Geneva, which seems bigger and bigger from a height.
You can also do a steep walk to have a panoramic view of the Mont Blanc!
Quite hidden in the scenery, there's a Buddhist temple!
Attention: First of all have a look at the opening times of the cable car! It's closed in the winter period.