OAZO, located directly opposite Tokyo Station North Exit, is a mixed commercial facility spreading along the paths connecting Marunouchi and Otemachi. It features an open atrium, many different artworks displayed in a galleria overflowing with light and a restaurant floor full of variety that combine to make it an "Intellectual Oasis Town". The underground pathways provide direct access to JR Tokyo Station, Tokyo Subway Station and Otemachi Station.

The shopping and dining area - located in the wide, open atrium space - is comprised of a variety of restaurants, shops and large-scale bookstores and is designed to become an amenity zone able to ensure visitors use their time spent in Marunouchi to the fullest. The atrium is shaped by OO Square, an indoor public space which features a large wall mural of Pablo Picasso's Guernika.

The OO Square is an open space located on the left just inside the 1F Entrance from JR Tokyo Station. The name "OO" comes from the "Maru" (Japanese for "Circle") in "Marunouchi" and the "O" in "Otemachi", and it was named thus in the hope that the area would become a bustling square connecting both towns and attracting large numbers of people.

The 80-year-old Marunouchi Hotel is located in front of Tokyo Station, the entrance hall to Japan. The hotel boasts 205 rooms designed using the principles of Modern-Japanism to provide guests with comfort and the excellent views the hotel is so proud of. The individually-tailored service provided by the hotel avoids giving guests that "large hotel" feel.