A longer, harder trip than Milford - but if you can fit it in, Doubtful is another of Southland's treasures.
The southernmost city in New Zealand - indeed in the entire British Empire. Notoriously cold, rainy and grey - but it has some nice brickwork.
The absolute bottom of the South Island, even further south than Invercargill, and therefore a tourist stop - though not a very long one.