Long downhill uses yamanote line

This picture is day of trying to find longdownhill place.We rode from Sugamo to Ootsuka. Almost of the way of road is downhill. But some road surface is rough and narrow. So here is not so good. May be, There are a lot of places in Tokyo for longdownhill where can climb by boarding on the train. Plese tell me good and confortable place to longdownhill.