depends on what you mean.
Iconic? Barton Creek Green Belt, maybe City Park.
easily navigable? CP first, BCGB main trail, second. However, the maintrail is packed with peds, dogs, and dogshit on the weekend. CP is a one way loop and well marked, but it's all rocks, all the time, moto trail, originally. used to be my favorite, but the fucked with it several years ago and I rarely ride there, now.
Brushy Creek is fun, but probably a hike, depending on where you're staying. not much elevation, but a little bit of everything (including yoga pants on the main paved path).
I know nothing of SATN. Kurdt, or Austinvines would have to chime in on that. supposedly pretty good.
bunch of unmentionables, but they are, like BCGB OFF the main trail, mazes with lot's of choices. loads of fun though. loads of climbing, too.
send up a flare if you want a guide. here lately, I've been soloing on sunday mornings. too much life happening with my crew.