Kansenji (観泉寺) is a Soto Zen temple which is a 14-minute walk from Seibu Shinjuku Line Kami-Igusa Station.
It was established in 1597, and its precincts are beautifully maintained.
There's a neat garden if you go inside the Sanmon gate. Hondo, or the main hall, which enshrines Gautama Buddha, is post-war reconstruction.
Kannondo, dedicated to Kannon Bosatsu, was relocated here in 1790.
Shoro, which a huge bell to tell time is hung, was erected in 1897.
If you walk toward south for 11 minutes from here, there is Ogikubo Hachiman Shrine. If you go west for 12 minutes, there stands Igusa Hachimangu Shrine. If you head south, 11 minutes of walk will take you to Ogikubo Hachiman Shrine.