We only saw the upper Duden Falls and were pleased with how the park was set up, good price (5 TL ea), well maintained. We also walked past the Lower falls but didn't stop to see them. We stayed in the old city and if going to either of the waterfall locations I would suggest a Taxi (about 30TL to the upper and probably close to 20TL for the lower).
We walked from the Old City to the upper waterfalls, it can be done, its about 15km, but it goes through the working sections of the city and you eventually run out of sidewalk to get you there and have to walk the road.
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