The low-down on Hidden Valley and its sand ripples from MAHLI. (Image at right has been rotated and contrast adjusted; click on link above or image for full-size version).
NASA description: NASA’s Mars rover Curiosity acquired this image using its Mars Hand Lens Imager (MAHLI), located on the turret at the end of the rover’s robotic arm, on August 4, 2014, Sol 709 of the Mars Science Laboratory Mission, at 18:21:39 UTC.
Sol 709 raw images (from all cameras), and Curiosity’s latest location map.