Derik Hammer discusses spanning an Availability Group across multiple sites:
In the architecture above, replica A and B are in the primary data center while replica C and D are in the disaster recovery (DR) site. Like the previous architecture, the disks are displayed as local but the most important part is that they are physically separate. SANs are wonderful systems with a lot of redundancy but they can also be a single point of failure. Keep your Availability Group disks separate.
This is a nice architectural overview. Once the series is done, it looks like it’ll be a good resource to discuss high availability and disaster recovery with management and show the options and trade-offs.