The Cydonia region of Mars seems to be chock full of weird anomalous structures. Southwest of the infamous "face" is a group of features that have been called "pyramids" (above right). With their relatively smooth, triangular sides, they bear a striking resemblance from the air to the pyramids at Giza, Egypt (above left).
One of the most closely studied is the so-called D&M pyramid. According to researcher Mark Carlotto, "the three illuminated faces of the D&M appear to be relatively flat with well defined edges in between.

Buttress like structures at the base of several edges are also evident. In the MGS image the edge between the northeast and northwest faces resembles a spine running from the apex of the D&M down to the ground. At the base of the spine lies a circular depression, possibly an opening. A dark feature seems to emanate northward from this depression or opening, which then leads into a sinuous channel off to the right."

Carlotto also has examined "the City Pyramid," a five-sided structure whose spines "resemble the five pointed Egyptian symbol for a star." In the most high-resolution photos of these structures taken by MGS, the pyramids look somewhat less pyramid-like, but their geometric shapes are still intriguing.