On my recent less than 12 hours in downtown Salt Lake City, I had to plan my time SUPER carefully. I wanted to see as much as possible and I only had like 6 hours in the city.
I took a shuttle straight from the airport to the Salt Lake Visitor Center to catch the US Bus Tour. This was a great hop on hop off bus that showed some great sights. I had also purchased the Connect Pass so that I could get off and see almost any of the sights along the way.
My main stops were the Hogle Zoo and the Lion House for lunch. I had a blast and only wished I had a few more hours to tour a few more spots. Still, a great afternoon!