There is a Edo-Tokyo Museum in Ryougoku.
You can enjoy to see the culture and history of through the 400-year history of Edo-Tokyo since Tokugawa Ieyasu entered Edo.
When I passed the museum, there were many people aroud it.
Next door to the museum is the Kokugikan(Sumo Hall).
The day I was there, it was a Sumo competition, there are three competitions held every year; January, May and September.
In the Ryougoku station, there are many photos of Yokoduna(Grand Champions) .