This is the entrance to the Tokyo Disney Resort's second theme park, Tokyo DisneySea. The buildings in the background are part of the Mira Costa Hotel which is actually inside the park. Guests walk through an archway below the hotel to enter the main area of the park.
Here is the view as you are walking underneath the hotel.
The park's main icon is Mt. Prometheus. An attraction called "Journey to the Center of the Earth" is located inside the volcano and at it's base is Fortress Explorations. The guide book describes the fortress as, "an interactive play area that includes plenty of wondrous scientific instruments and a recreation of a Spanish galleon. I am sometimes tempted to call it the "Tom Sawyer Island" of this park, but that really would not do it justice.