A blank rectangular canvas fills the browser viewport, rendered as a single rounded rectangle. The visualization demonstrates the foundational step of setting up an SVG drawing surface with D3 v5. The code uses `d3.select` to access the SVG element and sets its width and height attributes based on the document body’s dimensions. A `rect` element is appended and styled with `rx` for rounded corners, creating an empty, minimal display with no additional data or interactive elements.