How big Equestria supposed to be? Part 2

I just remember one thing - Grand Equestria Pony Summit. And this images:

This statue supposedly made from gemstones that summit delegates brought with themselves. IIRC one gem represents one major city that important enough to send said delegates on the summit. Which mean that it's not included towns like Ponyville, villages, farms, some other settlements...
It looks like Equestria have lots of major cities... Oliver estimation of Canterlot population of five hundred thousand ponies suddenly becomes far more believable for me :).