At http://phys.org/print326102164.html … we have two bubbles towering above and below our galaxy – see image (courtesy of NASA)
… and these are big bubbles seen together with the flat plane of the Milky Way. They stretch tens of thousands of light years in either direction. They were discovered just four years ago via Fermi, the Large Area Telescope. An article in Astrophysical Journal (accepted) says the outlines of the bubbles are sharp and the bubbles themselves glow in nearly uniform gamma rays like incandescent bulbs screwed into the centre of the galaxy. Not only that, it is at the furthest reaches of the bubbles that the highest energy appears to lie.
Earth bound telescopes could not see the bubbles. Most of the gamma rays are screened out by our atmosphere – so it wasn't until there were orbiting gamma ray observatories such as Fermi that anyone knew of their existence.