The C4 Model provides simple abstractions for documenting and communicating software architectures visually.
Here you can find a palette with shapes/nodes for the yEd Graph Editor to create diagrams with the C4 Model.
Go to Edit > Manage Palettes ... and then click Import Section to select the C4 Model.graphml file.
You should find the C4 Model in the list of available palette sections.
Level 2: Container Diagram (original)
