This is the description NASA/JPL/Arizona University give to this map strip of Mars taken February 19, 2008. “Caught in Action: Avalanches on North Polar Scarps” http://hirise.lpl.arizona.edu/PSP_007338_2640.
What they fail to mention is the Tube System that has been exposed and damaged by the avalanches. (A)
The black and white map (B) (Image credit: NASA/JPL/University of Arizona) includes a scale measurement line. This map strip of Mars is 6750 Meters / 4.19 miles wide and 33,200 Meters / 20.6 miles long.

Mars had most of its atmosphere stripped away approximately 450,000 years ago by a Planet that comes into our solar system every 3600 years called Nibiru/Wormwood/ Planet X. The civilizations that once called Mars home packed up and left. The resulting cataclysm caused their cities to be buried in layers of sediment.
What you are looking at in this series of images taken by the NASA HIRISE orbiter is an area that plainly shows the layers of sediment and what lies beneath.
Mars has an underground Tube System that resembles many “lungs” connected by Tubes of various diameters.
The main Tubes have a large diameter and reduce in size as they branch off to service access to areas of habitation - cities in large caverns, supply caverns, troop quarters, mining equipment storage, various craft, for offensive and defensive purposes, etc…

The blue “T” shape is (D), in actuality, a partially exposed Tube transport structure the inhabitants use to travel and transport material through. To give you an idea of size of transport Tube, the bluish "T" shaped object, the top of "T" from side to side is @ 400 Meters/ 1312 Feet. The "I" part of the "T" is @ 150 Meters / 492 feet. (C)
In the center of the “T” is an Intersection “Ball” that has a rupture and is under repair. Sand is flowing from top and right lower area. (D)

To the left side of the “Ball” are structures that look like “gallows” on top of the Tube (E) (F).
There appears to be a cavern behind these structures (F).
Looking further left, there are more structures and machines visible in this area. (G) (H).

To the right of the "Ball", a Detour Tube is under construction. (I) (J).
In the middle of the Detour Tube, sand/material flow is visible and is covering the recent construction (K).

The dark section toward front of Detour Tube is in process of construction and bluish metallic reflections are also visible. (L)
The Detour Tube will connect with the ruptured “Intersection ‘Ball’ when completed and the entire structure will be buried under a layer of sand.