There’s so much going on here it’s hard to know where to start. Basically, Stéphane wanted to get the darkest sky possible for this shot. So he went to the Atacama desert in Chile, not far from the Paranal observatory. At that latitude, and at that time of year, the Milky Way — usually seen as a band of light across the sky — circles the horizon! That glow you see around the picture is not from cities or anything else like that, it’s from the galaxy itself.
Since the Milky Way is so low in the sky, its soft light is minimized. He also took this picture at new Moon, so there was no light from that, either. Zodiacal light is sunlight reflected back to Earth from dust in the plane of the solar system, and he chose the time of the picture to minimize that as well.
The glow you can see in the picture is called gegenschein, and is sunlight reflected back to Earth from particles in the solar system, but this light is more concentrated in the area of the sky directly opposite the Sun’s position. That’s why it appears so bright in that oval, and fades away to the sides.
What Stéphane has essentially achieved here is a picture with the darkest sky possible.