Ueno Zoo is only a few stops away from Tokyo  mainline station on the JR line. The entrance fee for the whole zoo is 600 yen per adult which we thought was ridiculously cheap. Ri Ri and Shin Shin are close to the main entrance allowing you to just see the giant pandas if you wish. 

The zoo opens at 9.30 and we would recommend going early to avoid the queues. 

Enjoy!