Tetsugakudo Park (哲学堂公園, Tetsugakudo Koen), located to the west of Shinjuku, is a municipal park which was founded by philosopher Inoue Enryo (1858-1919) in 1906. This park was created based on his philosophical perspective.
There are 11 small buildings designed by him left in the park. Usually, the interiors of the buildings are not disclosed, but from April 29 to May 5, on weekends and national holidays in October, and on the first Sunday of every month, some of them are disclosed.
It's a 12-min walk from Seibu Shinjuku Line Araiyakushi-mae Station, or a 13-min walk from Toei Oedo Line Ochiai-Minaminagasaki Station.
The Tetsurimon Gate, constructed in 1909, houses under its roof statues of a tengu and a ghost instead of a pair of Nioh. (No are Bhuddist deites often guarding the entrance of a temple.) Tetsurimon means "gate of philosophic doctrine."
Shiseido is a shrine dedicated to Buddha, Confucius, Socrates and Kant, who are sages in philosophy. Two of them are from the East and the other two are from the West. It was created in 1904. A statue of Buddha is placed inside. Shiseido means "hall for four saints".
Rokkendai, erected in 1909, is a tower dedicated to six sages of the East - Shotoku Taishi (Prince Shotoku) and Sugawara no Michizane from Japan, Zhuangzi and Zhu Xi from China, and Nagarjuna and Kapila from India. Rokkendai means "tower for six sages."
Uchukan, literally meaning the universe hall, was created in 1913 as a lecture room for philosophy. In it stands a statue of Shotoku Taishi.
Zettaijo, which means "the absolute castle", was completed in 1915 as a library.
Sangakutei, created in 1909, enshrines three great Japanese scholars - Hirata Atsutane on Shinto, Hayashi Razan on Confucianism, and Gyonen on Buddhism. Sangakutei means "gazebo for three great scholars."
Mujinzo was a museum built in the early 1900s. Mujinzo means "infinite storage."
Dokuroan was a resting house constructed in the early 1900s.
Sansoen is dedicated to the Yellow Emperor of China, Aksapada Gautama of India, and Thales of Greece. Sansoen means "garden for three founders."