Polyterrasse Zurich is a large terrace with panoramic views over Zürich city. The terrace itself is not particularly attractive. But the views are great and it's a nice place to get an overview pic of Zürich city.
Since it's located directly in front of the ETH Building, it's a popular place for student to meet. They often have food trucks here at lunchtime.
Location: Leonhardstrasse 34, 8001 Zürich
You can easily reach Polyterrasse by riding the Polybahn funicular from Zurich old town. You can use regular Zurich public transport tickets to ride.
Or you can walk up the stairs on Schienhutgasse, if you don't want to pay for a ticket or want more fitness.
After your visit, you can explore nearby attractions like the Zoological Museum.