Sanya(山谷) is an area name at the northeastern part of Taito district(台東区) in Tokyo.
And Southern part of the Namidabashi(泪橋) intersection.

I think its the slummiest spot in Tokyo.

When I was young I’ve been there many times; daytime until midnight because I was living there nearby.
I could still remember, it was midnight, I saw people doing bonfire on the center of the street while they were drinking and screaming something strange.
I couldn’t believe what I saw.
Is this Japan?
I heard from someone about Sanya.
According to him that people in Sanya do sex on the street even with same gender.
It’s surprising!
What’s more, they deliberately try to hit the car with their body to get money from the drivers.

Source of a Quote Wikipedia Sanya Doyagai(ドヤ街)

A neighborhood named “San-ya” existed until 1966 as Sanya Asakusa Taito district.

Source of a Quote Wikipedia Sanya Tamahime Park (玉姫公園)

Now there is no ‘placed named of Sanya’.
But until now people who remember the old times and old things, they still call this area ‘Sanya’.

You can see Sanya’s situation from this YouTube video.

It also became a background location of an anime series and movie “Ashita no Joe (あしたのジョー)’ or “Tomorrow’s Joe”.

Ashita no Joe 2 THE MOVIE Trailer.

Another part of this area was called “Yoshiwara yukaku(吉原遊郭)” because it was located at the red light district.
During those times many casual laborers stayed/lived there because of there were many cheaped accommodation surrounding the area.

SANYA, Tokyo, Broken city

Since 2000, it has become popular place of foreign backpacker because of easy access to public transportation and there are many cheap hotels available.
Some tourist said, it’s good because it’s more quiet than Shibuya and they recommend some hotels.
I’m going to introduce some reasonable hotels⇒HERE!

And there’s similar place in Osaka too.
I think that it’s maybe more dangerous.
We call that place ‘Kamagasaki(釜ヶ崎)or Airin district(あいりん地区)’.⇒About this.