The Sumatran tiger outdoor enclosure at Frankfurt Zoo has got an open-top bar-less design. The tiger enclosure has one viewing window that attracts the public as well as the big cat. The tiger is pacing up and down in front of the window at the time of my visit. Most probably the feline is waiting for the zookeeper to arrive with food. But this time the wait will be in vain, because it is its fasting day according the information panel.