Koishikawa Botanical Garden
Koishikawa Botanical Garden (小石川植物園) is a garden in Bunkyo managed by the University of Tokyo. It exhibits and preserves many tree and plant species and includes a traditional Japanese landscape garden.
todai
University of Tokyo (Todai)
The University of Tokyo (東京大学; Tokyo daigaku), often abbreviated as Todai (東大), is the most prestigious university in Japan. Its main campus is in Hongo (Bunkyo). As far as I can tell, although there are guards at the gates, it can be entered pretty much freely.