landlimo

This one comes apart cleanly, and it comes apart from the right. Limo is the head - a landlimo is a kind of limo - and land- is there to say which kind. That is the whole of the head-final rule set out in compound words, and the reason a learner who has met lando and limo needs no dictionary for the third word.

Limo on its own is any boundary: the edge of a field, the limit of your patience, the point past which a joke stops being funny. Adding land- narrows it to the political line on the map, with the customs post and the queue and the stamp in the passport. Esperanto builds several of these on the same head: urbolimo the city boundary, tempolimo a deadline, rapidlimo a speed limit.

You will also see landolimo, with the linking -o- left in. Both are correct and both are used; the compounding article explains when the vowel earns its place, and the short answer here is that landlimo is pronounceable without it, so most writers drop it. The adjective is landlima - a landlima town is a border town.