Young massive clusters form from massive clumps of gas and dust that collapse under their own gravity. These clumps must be massive enough that their escape velocity exceeds the sound speed of ionized gas in order to continue collapsing into a cluster. Observations of nearby galaxies have detected progenitors of young massive clusters that are dense, massive clumps of gas and dust. However, similar progenitors have so far evaded detection within our own Milky Way galaxy.