Hello WanMil,
admin_level=7 just an example. admin_levels are used differently in countries and in regions etc.
I see "Verbandsgemeinde Waldmohr" http://www.openstreetmap.org/browse/relation/897709 which is the only boundary that has admin_level=7. The interesting thing is: the returned result-list for this boundary is always empty. So, maybe there is a cheaper way to detect this first or does it means that there is a bug in quadtree or the selection of the boundaries?
Sounds more like a bug! But it's also possible that the higher admin_levels (8,9,10,11) references all other admin_levels and therefore there all elements of Waldmohr have been removed before querying for it.
hmm, I think you missed the point that we start with lower admin_levels: // Reverse the sorting because we want to start with the lowest admin level Collections.reverse(boundaries); and I found Waldmohr because it prevented the elements from being "fully worked out". So, I agree that this seems to be a bug. By the way, I use your bounds from europe_bounds_20111106.zip Ciao, Gerd