I recently found out that the kanji 洛 is associated with Kyoto / the capital.
Here are some example words showing this association:
洛内【らくない】 : "in Kyoto or the capital"
洛外【らくがい】 : "outside Kyoto or the capital"
洛南【らくなん】 : "southern part of Kyoto / south of the capital"
I figured it must be from the time when Kyoto was Japan's capital, but I've been unable to find where the relation between 洛 and "capital" comes from.
Could it be similar to how, for example, 米 is associated to America, and 亜 with Asia? Maybe 洛 was used to write "capital" or "Kyoto" at some point?