A guided walk through the nested levels for Barcelona. Neighbourhood. City. Region. Stop. Then look up at the limits above.
The narrated version of the aggregation atlas: the nested levels, a neighbourhood inside the city inside the region, read step by step, for anyone meeting the Index without slides. Each step shows what the people at that level log in a typical month, how often it lands, and the sentence that hands off to the next level. A status pill on each step marks its data as partial (some real Barcelona feeds) or mock (sample values). Step 3, the region, is as far up as the adding goes. Below that line, steps 4 and 5 shift into the limits register: italic, lower density, read as observation, not adding up.
The walk takes a minute and a half. It is the version a mayor, a lab lead, or an outside reviewer can be talked through without slides. It is also the test of whether stopping at the region holds up: by the time the walk stops at the region, the reader should already know why the next two levels are watched, not added up. If they do not, the page has failed.
↪ Return to the aggregation atlas · drill into the embedding prefix relationship · or examine the per-pillar transition rules.