The last decade has brought the discovery of a large number of massive (M > 10000 M?) young open clusters in the Milky Way, which had previously not been thought to exist. I will present a brief review of these discoveries, with strong emphasis on the use of these clusters as astrophysical laboratories. I will also present the very recent discovery of a number of massive clusters concentrated towards a small region of the Scutum Arm, providing evidence for the existence of starburst activity on a much larger scale than previously assumed.