Until noon each day cars descend the slope; after noon they climb—a reversing one-way street. Probably the only such place in all Japan is the street known as "Kagurazaka-dori" (formally part of Waseda-dori). It is the slope climbing from JR Iidabashi Station West Exit's Sotobori-dori intersection toward Bishamonten (Zenkokuji).
From Takebashi Station on the Tokyo Metro Tozai Line, where Palaceside Building stands, get off at Iidabashi or Kagurazaka and you are there.
Why it became a reversing one-way street has several theories, but the strongest is former Prime Minister Tanaka Kakuei's "crane's single word." One-way traffic ended congestion and made travel between his Mejiro residence and the Diet convenient—or so the story goes. Others say a fine person lived in Kagurazaka and commuted to the Diet from there.
The street is quite narrow, with delivery trucks parked constantly for unloading—two-way traffic is effectively impossible. Traffic volume differs sharply morning and afternoon by direction, so Kaku-san's (?) wisdom deserves a "as expected..." perhaps.
Kagurazaka strolls are popular with seniors and young women. Watching the direction change on Kagurazaka-dori at noon might be fun too.