San Francisco, California
You just can't miss. We definitely used the transit pass enough to pay for the entire booklet (at $6 a cable car ride), meaning the other things were all icing. And what icing! Spent 5 hours at the Academy of Sciences, loved the Aquarium and Exploratorium, enjoyed the nearly obligatory cruise of the Bay, and made sure to take advantage of $20 off the incredible Go Car tour experience. Seriously hundreds of dollars of value for the $69 we spent per. Absolutely essential starting point for a SF trip!