What is wrong with discussing Torah? Say what you can and be clear that there is more to it.
One interesting Halacha of a city is that it is always square/rectangle. If a house sticks out of the others, you extend the imaginary city wall until after 70 Amos from that house. Also, if you have three towns in a setup of a Segol and one of them fits between the other two, you view it as if it is there, and if that would fill the gap of 140 Amos on both sides, all three are considered one city.