Multiple Kubernetes clusters can be managed as a single cluster with the help of federated clusters. So, you can create multiple Kubernetes clusters within a data center/cloud and use federation to control/manage them all at one place.

The federated clusters can achieve this by doing the following two things. Refer to the below diagram.

https://platform9.com/blog/kubernetes-federation-what-it-is-and-how-to-set-it-up/