This is where the Hokage's offices are located. Also, the bulletin board which lists all of the available missions, that will be updated almost every day.
Academy Students come here to learn the basics of becoming a ninja. A graduation exam will take place after the course of the lessons in order to allow them to graduate to see if they are ready to become a Genin. Amiya Chinatsu (the current Hokage) is often seen around the classrooms inspecting the staff to make sure they are living up to their expectations in teaching.