Saturday I rode with a group from work just to tackle a hill I knew of on Burton Hill Road near my parents house.  You can get almost all the way to Burton Hill on the Trinity Trails.  One of the guys had a GPS and reported it was 15%, with portions up to an 18% grade.  It's about .3 miles from bottom to top.  Turn right (west) at the top onto Byers, and then bear right off Byers onto Roaring Springs and put it in high gear and do 40 for about a mile or so.  You can cut through the neighborhood at the bottom of the hill to get back to Burton Hill and repeat if you really want to give yourself a workout.  It's almost as tough as The Wall on the Paluxy Pedal ride, just shorter.  I used to do this hill regularly when my brother was racing and I went on training rides with him (30ish years ago).  Our group Saturday left from downtown and I think it was about 20 miles round trip - I haven't checked my computer.  Sounds like a good evening training ride if I bring my bike with me and leave after work around 4:00.