Shinozaki Sengen Jinja (篠崎浅間神社), founded in 938, is a Shinto shrine whichis a 13-min walk from Toei Shinjuku Line Shinozaki Station.
At this shrine, a festival called the Hata-matsuri is held from the end of June to July 1 every two years.

Hata-matsuri at Shinozaki Sengen Shrine

Shinozaki Sengen Jinja holds the Reitaisai (例大祭), or the Annual Grand Festival, from the end of June to July 1. At this occasion, in the even-numbered years, ten tall flags (nobori) are erected in the shrine precincts by hand, thus called the Nobori-matsuri (幟祭) as another name for this festival. This process takes the whole morning of the last Sunday of June.
Rituals themselves (and other events) are held not on this day but on June 30 and July 1.

Poles of the flags are carried into the precincts one by one.

Each wooden flag pole, which is set up by the hands of many participants using a rope, is 22 meters (72 feet) log and weighs about 1 metric ton. It takes about 30 to 40 minutes to set up a flag.

The meaning of the words written on the flag is "for the deities of the Sengen shrine." In theory, these flags are thought to be the objects for the divinities to descend from the sky (though probably most people are not conscious about this.)

Ohayashi is played during this event.

Taisai

As aforementioned, rituals and other votive events are not held on the day of the flag pole erecting (unless the last Saturday of the June is the 30th day of the month) but are set on June 30 and July 1, regardless of what days of the week they are.