The record sensitivity of the X-ray survey performed by the Spektrum-Roentgen-Gamma Observatory makes it possible to discover very rare and unusual X-ray sources. After the recently completed third all-sky survey, astronomers identified a gigantic, “round” object, named G116.6-26.1, with an angular size of 8 times the Moon or a physical size of truly astounding 600-700 light-years. The authors of the discovery believe this to be the remnant of a thermonuclear supernova, which exploded some 40,000 years ago. The source is located high above the plane of our Galaxy, most likely in the hot, low density gas of the Milky Way halo. Such an unusual environment makes the remnant almost ten times brighter in X-rays than naive models would predict. This and similar remnants (if more are to be found) open a new way of probing the elusive hot gaseous halo of our Galaxy.