This visualization displays population trends across Aragon's counties over time, using a multi-line chart where each line represents a different county. The data, loaded from a CSV file, is filtered to show the central region. The implementation uses D3 v7 with a custom `linePlot` module, employing scales like `scaleTime` and `scaleLinear`, along with `d3.line` and `d3.axisBottom`/`d3.axisLeft`. An interactive tooltip appears on mouseover, though its data-point lookup logic is incomplete.