Cloud computing has ushered in a new class of hyper-scale systems, characterized by large-scale distributed systems, global connectivity, and ubiquitous computing models that span the spectrum from centralized data centers to the edge. Powering these hyper-scales are global networks that connect end-users through various other networks and devices to the cloud. In this talk, we describe our journey in building the network of one of the biggest cloud systems, Microsoft Azure. This network is built out of 130K+ miles of terrestrial and subsea cables,  processes an average of 30 billion packets/second, and interconnects with more than 20K peering points around the globe. We describe many of the technological and engineering building blocks that enable us to build and reliably operate this network, including innovations in fiber optics, software-defined networking, network design, switch software and global-scale monitoring, and simulation software.