This circular feature is a collection of hills, with some connected by ridges.
The circularity suggests that perhaps there was once an impact crater here that was subsequently filled with material which was somehow more resistant to erosion than the landscape around it.
Over time, as erosion stripped away the ground, the fill material was left standing higher (although it has clearly been eroded as well).
Written by: Ross Beyer (8 April 2009)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_012425_1455
Image: NASA/JPL/University of Arizona