Find it difficult to believe that any zoo trip to Tokyo would not include Ueno. When I went there 7 years ago only an odd exhibit struck me as "dismal",then again,I love city zoos. The truth is that it is packed with interesting things and is most certainly a "full day" zoo. To go to Sumida and not Ueno strikes me as bizarre ,I would apply the same rational to Tokyo Sea Life..which is at the very least a 4 or 5 hour visit time.