Just a basic question: But how do you figure Teleportaion Circle is so much of a problem?

1)Spellcasters. You'd need a 17th level plus spellcaster to cast Teleportation Circle. Even if you were to have a massive magical empire, there won't be more then 25 or so spellcasters of that level around. So you have a problem simply casting the spell.

2)Permanency. Again you'd need the 17th+ level spellcaster to cast a permanency and the teleport circle. At the most a single spellcaster could make five such circles a day, at a cost of 5,000 gp and 22,500 xp. That's enough for a spellcaster to loose a level as it's less then 20,000 between levels at the high level end of the chart.

3)Military Attacks. A teleport circle can only send a couple troops at a time. Everyone that can fit in a five foot circle. This is not a good way to get an army into a city. Even just getting a small strike force in will take some time.

4)Trade. A teleport circle can only send a couple creatures and their maximum load. So you can't teleport wagon loads of materials. It would be a slow process to have several people pick up what materials they could and teleport back and forth.

5)As noted in the Teleport spell description, 'areas of strong physical or magical energy may make teleportation hazardous or impossible. Now, granted there are no rules for this, but at least it is in the rules. You also have to take into account magical defenses.

In the end Teleport does not look practical for warfare or trade. Yes, they both have their uses, but not all out world changing.

And if your going from 'teleport' as existed from the dawn of time, then defenses will have existed too. So you'd have equally powerful and permanent anti-teleport area spells to block such effects.

Now, I don't mean to tear down your whole 'mega city and wastelands', I'm just pointing out that saying teleport circle is a world changer does not work out.