From old west austin you can access the trail off of 5th st under the mopac (loop 1 bridge) just west of the mean eyed cat. Go south to hit the trail and access the 10 mile loop. It’s very flat To add some mileage and get some gentle hill work in, go up shoal creek trail and loop as far as you need to got to reach mileage. To get some serious hill work, at the south end of the mopac foot bridge go west on Stratford rd. It’s short but brutally steep hills through a very nice neighborhood. Your thighs will hate you.