I hiked Seminole Canyon via the Rio Grande Trail back in 2008 and was impressed by it. The only drawback was that the trail was fairly boring until the very end and then, WOW! You were provided with some breathtaking views of the canyon and river running through it.
Since I was in the general area, I decided to swing by Seminole Canyon again, mainly to camp overnight. However, I was pleased to learn that a new trail had been developed about a year ago called the Canyon Rim Trail. Naturally, I couldn't resist hiking it. :)
The Canyon Rim trail provides many more scenic overviews of different parts of Seminole Canyon and also takes you out along the banks of the Rio Grande River. The trail is well marked with huge rock cairns and is easy to follow. In my opinion, this new trail is the best thing this State park has done. It really shows off the natural beauty of the area. Good job, Texas State Parks!