Ueno Park (上野公園) is located close to Ueno Station and is a huge, public park. You’ll never get bored of this park as it’s filled with museums, temples, a zoo and more. Ueno Park is great to visit all year round. You can rent Swan Boats, enjoy nature and on Sunday you can find many artist playing instruments, sketching portraits, doing magic shows and so on. During the Sakura period (late March, early April) it can be very crowded as Ueno Park is one of Tokyo’s most popular Hanami (cherry blossom viewing) spots, with more than 1000 Sakura Trees.
It’s recommended to combine your visit to the park with a visit to one of Ueno’s many museums. Especially the National Museum of Nature and Science and the Tokyo National Museum are worth a visit! Another famous spot of Ueno Park is Ueno Zoo, which is the oldest Zoo in Japan, build in 1882.
If you love Japanese Temples and Shrines, be sure to make a stop at the Kaneji Temple, Kiyomizu Kannon Temple and the Toshogu Shrine. All of them have no entree fee and no closing days. All the Temples, Shrines, Museums and the Zoo are easily to find, thanks to the maps placed all around Ueno Park.
Official website (in Japanese): http://www.kensetsu.metro.tokyo.jp/toubuk/ueno/index_top.html