A line chart displays a week of temperature readings across multiple cities, with each city represented by a distinct colored line and a corresponding color legend. The visualization uses d3.nest to group data by city, d3.line with curveBasis for smooth paths, and d3.scaleOrdinal with schemeCategory10 for color mapping. Data comes from a CSV file loaded via d3.csv, rendered as SVG with axes from d3.axisLeft and d3.axisBottom.