The Tobu Railway Musuem is dedicated to the history of the Tobu Railway. It opened in 1989 and was refurbished in 2009.
Under Higashi Mukojima station (Sumida) on the Tobu Isesaki line from Asakusa.
The following locomotives are on display:
5 (B1 steam), 6 (B1 steam), ED101, ED5015, ED4001, plus railcars/tram
In addition there are simulators, track level view, exhibits, models and shop.
Wikipedia web page
Museum website (Japanese)