"I passed by the intersection."
Am I the only one who has trouble typing "n" kana after "ん?" If I type "こうさてんの" my computer always ignores the second "n" keystroke and gives me "こうさてんお." The easiest solution is to (wrongly) type a third "n," like this: k o u s a t e n n n o. I can't imagine that's how Japanese people do it.
It's not really a "third" n, it's more of a double n to make sure that you're not typing na, ni, nu, ne, or no.
If only one n meant ん, then typing "no" could be interpreted by the computer as either "んお" or "の". And then, "nno" could be "んの" or "んんお".
The ambiguity is solved by making nn = ん when typing