Q. The cheapest fare I can find to Cambodia involves a plane change in Shanghai. The wait time is 23 hours. First, is it permitted to leave the airport and tourist around in Shanghai without a China visa for a few hours? Second, what would be a "do not miss" activity/attraction for that time?
A. As long as you're holding a ticket onward, and not staying longer than the allotted 48-hours, you'll be fine. From the Chinese Consulate: Visas are not required of passport holders of the following countries, who transit through Pudong Airport or Hongqiao Airport of Shanghai, provided they hold valid passports, visas for the onward countries, final destination tickets and have booked seats, and stay in Shanghai for less than 48 hours: Republic of Korea, United States, Canada, Australia, New Zealand, Germany, France, Netherlands, Belgium, Luxemburg, Portugal, Spain, Italy, Austria, Greece, Sweden, Denmark, Norway, Finland, Iceland.
As for what to do during your stay, there's plenty! You'll find a thorough to-do list of Shanghai's Greatest Hits on TripAdvisor. The Shanghai Museum is always popular, as is the Urban Planning Exhibition Hall. Even a little after dinner stroll on the Bund is a pretty spectacular way to spend an evening.
Shanghai image via Shutterstock