JOINing planet_osm_point and planet_osm_polygon

Hi again,

so, my next problem…
I want to display the city boundaries of city/town greater that X and with more than Y residents.
Problem: the way must be read from planet_osm_polygon. Here I have the size, too, using

ST_Area(ST_Transform(planet_osm_polygon.way, 4326)::geography) / 1000000) AS km2

, but the population must be read from planet_osm_point.
Then my problem is to find a column in the two tables to make my JOIN…
I cannot use just “name”, since it’s not unique and if I do that, I get a size for a little city like “Biella” of 913 km² (in the real word, it’s just 46 km²)…

Any idea?