Designed for the C4 model
Structurizr is a collection of tooling to create software architecture diagrams/documentation, and specifically designed to support the C4 model for visualising software architecture.
Code, text, or UI?
Structurizr uses the concept of a "workspace" to group related diagrams and documentation. Workspaces can be created using a number of tools.
Document your cloud architecture
Use themes to help document your cloud architecture; with prebuilt themes for Amazon Web Services, Microsoft Azure, Google Cloud Platform, Oracle Cloud Infrastructure, and Kubernetes. See Help - Themes for more details.