there are a bunch of short, steep hills in the metro san diego area that are a good challenge to ride when you group 12-20 of them together. a bunch of them hit 16+% with several hitting 20+%. steepest one clocks in around 28%. most are about a block-2 blocks in length with groupings (3-5 climbs of adjacent streets or at least very close by). some days, you start motivated to hit them all but start the first climb and realize that it won't be that day. other days, you can't get enough. i credit a steady diet of the short punchy climbs with helping me perform (slightly) better on longer climbs in the 5-7% grade/2-7 mile range mentally and physically.