There's a region in the north of Syrtis Major Planum, which is very large. It runs, diagonally, from the south-east corner to the north-west corner on this map. There are what look to be many 'pyramid cities' running throughout the area and tons of other anomalies. I can't be sure it's all one area, although, it all *seems* to be connected.
If this is one large area, then it deserves more attention than Cydonia. It would seem to have been an important city, at one time. The landscape is strewn with what appear to be the broken remnants of a past civilization. Items which resemble pieces of broken statues, columns, faces, structures and even a sphinx or two, seem to be common among these pyramidal ruins.
The following is only one small area in this long 'chain' of ruins.