Shinjuku was just a village suburbs during the Edo period. Nowadays it is one of the two main economic centers of Tokyo, along with the Nihombashi-Otemachi-Marunouchi area.
Shinjuku has the highest concentration of skyscrapers in Japan and is the symbol of Japanese modernism. The Tokyo Metropolitan government moved its offices from Nihombashi to Shinjuku in 1991 in the renowned "Tocho" buildings, which main tower is still the highest in the capital (243m).
Shopping
Shinjuku is a paradise for shoppers. It has more department stores than anywhere else in Japan. The most famous are Takashimaya-Times Square, Isetan, Mitsukoshi, Marui, My City and Odakyu.
Big electronics shops are only more numerous in Akihabara. But Shinjuku boasts the biggest of them, such as Sakuraya, Yodobashi Camera and Bic Camera.
Music lovers will find their happiness at Tower Records and HMV.
Kabukicho 歌舞伎町
North-Eastern Shinjuku, beyond Yasukuni-dori is the famous red-light district called "Kabuki-cho". It is the entertainment district par excellence and one of the hottest places in Tokyo, with hostess bars, adult video shops, soap lands (massage parlours), strip bars and love hotels. Some Japanese will warn you that it can be dangerous, but you shouldn't be paranoiac about it, as Tokyo is still safer than most big Western cities.