Abell 2029

Abell 2029 or A2029 is a large cluster of galaxies 1 billion light years away in the constellation Virgo. 
Its central galaxy, IC 1101, is the largest galaxy known. Estimates ranging from 5.6 to over 6 million light years across. Contrast this with the Milky Way, which is 200,000 light years across. 
A2029 is also about 81 times bigger than the Milky Way, with a luminosity of 2 L☉. This type of galaxy may have grown to its large size by accreting nearby galaxies.