Why does Belgium shine so brightly?
Belgium's penchant for extravagant motorway lighting is suddenly in the spotlight thanks to pictures posted by French astronaut Thomas Pesquet.
The images of Europe taken from the International Space Station (ISS) have notched up tens of thousands of reactions on Facebook.
Belgium can be seen glowing more brightly than its neighbours.
The country's dense road network enjoys near-total streetlight coverage, with lights kept on throughout the night.
It uses about 2.2 million bulbs to illuminate Belgium's roads - with 186 bulbs per square mile, the New York Times reports.
The 39-year-old French astronaut posted an image on Twitter showing the Aurora Borealis - also known as the Northern Lights - visible towards the north of the globe, and also noted that Belgium "stands out as usual".
In another, on his Facebook page, he said London, Paris and Brussels "form a very European triangle".
The photos are taken from the "cupola" - a module of the ISS built by the European Space Agency.
In his blog, Mr Pesquet says he likes to look out on the Earth while working out on an exercise machine positioned there.
"There are not a lot of gyms with such a view!" he writes.
He describes in detail life on board the space station, explaining - among other things - that tortillas are better than bread in space, as they don't leave crumbs to plague the astronauts in their weightless environment.
Most social media responses to the images marvelled at the beauty of the Earth viewed at night from some 400km (248 miles) above.
But some complained about the wasted power and light pollution: "We can see very well the glitz and wasted electricity! Awful for lovers of the sky!" wrote Christian Cellier on Facebook.
And one user, Michel-L Saucy said, was more concerned about extra-terrestrial visitors: "Hope that the aliens are not too attracted to light... We cannot accommodate them all once!"