Yomiuri V Dori

The slope from the Tamagawa up to my house offers at best 20-25 meters elevation change, and only one short stretch that requires a low gear ... never even bothered to measure it precisely.  The "hospital hill" at Sakura-ga-oka and Tama Hills, is over 15 kms away and not very steep, as the grade gradually shifts from 2-3% up to 5-6% near the top.  Most of the hills in central Tokyo offer only short stretches, mostly no more than 100-200 meters long, so you barely get going before you stop.
James M. last year mentioned the climb to Yomiuri Land as a good training spot.  I tried it once but somehow it had fallen off my radar screen during my off time last summer.  I've stopped by twice in the past month, each time doing the climb 4-5 times as part of a short ride.  From the train station roundabout at the bottom to the top of the main climb is a little over 700 meters distance, and a little over 60 meters of elevation change.  There is a 9-10% grade, with a bit less at the very bottom and top sections.  Little or no traffic.  Other cyclists are there doing the same thing.  There are what seem to be Yomiuri Giants baseball fans hanging out at the back entrance to the ballpark/training facility near the top  ... they acknowledge your effort on your 3rd and subsequent climbs.  And a big plus for the Giants fan (not me), the roadside is lined with flags, one marking each Giants victory this past season.  Maybe even better motivation for any Hanshin fans. 
Highly recommended for training.

The hill to Yomiuri Land.  Does not look like much viewed from Tamagawahara-bashi

This view from the bottom of the climb.  It continues around a curve to the right.

Directions:  Cross the Tamagawa from Tokyo at Tamagawahara-bashi (the road to One-Kansen, Tsurugawa Kaido - Rte 19).  Continue across Kawasaki Kaido (Rte 9 - the major crossing just after going under the train tracks within 500 meters of the river), then turn left at the next signal onto Rte 124.  Proceed until you go under the Keio tracks and turn left into the roundabout on the South entrance of Keio Yomiuri Land Station.  In the photo above, you can see the station platform on the left edge of the photo.  Climb and descend.  Climb and descend.  Repeat until you wilt.