In this chapter, I review studies of the three massive young clusters at the Galactic Center—Arches, Quintuplet, and the Young Nuclear Cluster. These clusters reside in an extreme environment and are ideal laboratories for studying how such environments influence the star and cluster formation process and subsequent cluster evolution. The emphasis in this chapter is on the observational constraints on the cluster properties including the stellar content, initial mass function, orbit and birth location, and internal dynamics. I place these clusters into the context of our understanding of star formation. I also describe observational methodologies needed for studies of these clusters and I finish with open questions that can be addressed with both current and future observational facilities.