You can visit CERN if that's your kind of thing - tram 18 from the centre goes there, it's the last stop so nice and easy. It has a visitor centre and can have more in depth things if you book in advance.
Walking along the lake is lovely, a great way to spend an afternoon.
There is also a world heritage site vineyard along from Geneva, wind has been made in that region since Roman times, that was stunning. I've attached a couple of photos from my last visit. I can try and find the name of the place in the morning, but it's on the world heritage site list (searchable by location and map).