downtown has a good amount of spots. there's a pretty famous ledge spot, jackson 5 that is just about perfect.
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the downhill parking garage ledges in this video are somewhere in downtown.
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this ditch is just a little south of downtown on interstate 30. same one fred gall ollied into in the intro to his photosynthesis part/had a photo of.
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there's also a lot of spots in fort worth but, it's about 20-30 minutes from dallas. here's a natural qp though....
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that's all i can think of for now... if you want to you can pm me for directions/more spots. have a good one, hope this helps.