NTT DoCoMo Sumida Building

Completed in 2004, this 27-story, 133.7-meter (156 meters including antenna) office building in Yokoami, Sumida serves as a key operational hub for NTT DoCoMo's mobile network, and houses a permanent exhibition tracing Japan's mobile communications history.

Use

Office tower

Area

Sumida City

Completed

2004

Floors

27 above ground, 2 below

Height

133.7 m

Developer

NTT DoCoMo

Architect

NTT Facilities

A Telecom Tower Standing Watch over Ryogoku

At 1-9-2 Yokoami, Sumida City — near the Kokugikan sumo arena and the former Yasuda Garden — the NTT DoCoMo Sumida Building was completed in June 2004. Designed by NTT Facilities, the building rises to 27 stories, reaching 133.7 meters in structural height. When the antenna mast atop the building is included, the total height reaches approximately 156 meters — a distinctive silhouette visible from considerable distance as one walks through this part of Sumida.

NTT DoCoMo operates similar operational buildings in Tokyo, Osaka, and Nagoya, each serving as an infrastructure backbone for the mobile network. The Sumida Building plays a role in maintaining coverage across eastern Tokyo, hosting the technical and administrative functions that keep mobile signals flowing. This building is a reminder that behind every smartphone connection, somewhere nearby, there is hardware like this quietly running.

The History Exhibition That Tells a National Story

Beyond its operational role, the NTT DoCoMo Sumida Building houses the NTT DoCoMo History Exhibition Square — a permanent display tracing the arc of Japan’s mobile communications industry. From the enormous shoulder-bag-sized car phones of the 1980s to the pocket-sized smartphones of today, the exhibition walks visitors through decades of technological change using actual handsets and network equipment.

The contrast is part of the appeal: from outside, the building presents as a purely functional structure; inside, it contains a curated museum of the technology that reshaped everyday Japanese life. The telecommunications industry — invisible by nature — finds a rare moment of tangibility here.

Summary

The NTT DoCoMo Sumida Building was completed in 2004, rising 27 stories to a structural height of 133.7 meters (approximately 156 meters including the antenna mast). Designed by NTT Facilities, it anchors an important node in eastern Tokyo’s mobile network while offering, through its History Exhibition Square, an unexpected window into the story of Japan’s mobile revolution. On a walk through Ryogoku, try viewing the building from the former Yasuda Garden side — the antenna tower gives it a presence that outlasts a simple first glance.

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