This condominiums are called "Gunkan" or "Warship" because of the shape of the rooftop.
I don't know what's inside of that part but it looks like a bridge of the warship.
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<The Nearest Station>
Higashi Shinjuku station on Oedo Line / Fukutoshin Line
(E02/Toei Subway/F12/Tokyo Metro)
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I found an impressive art at the entrance of another building near here.
