10'000 people in 600x600 meters is INSANE! That would be 27'800 residents per square kilometer: our world top 3 highest density cities have 21'000, 18'900 and 7'900!
Did not expect a Czech Fortress Design. yeah a fort like that is really durable on a siege as long as the enemy doesn't 1)pollute and/or poison the waters and 2) destroy and occupy the supply route.