If you hear about Franz Josef Glacier, Fox Glacier might be mentioned as well. These two glaciers are like two peas in a pot but it looks like Franz is stealing the spotlights in most cases. But as both glaciers are massively retreating these days the only way to get a good sight of the glaciers now is on a helicopter tour (hiking up to the foot of the bottom of the glaciers is forbidden nowadays)
If you are deciding to make a stop in Fox Glacier and you want to explore the area, then Lake Matheson is worth a visit, preferable in the early morning when the clouds have not closed the curtain over the Fox Glacier. The fairly easy loop gives you some nice viewpoints of the area. Another great spot (if you got the time for the detour) is Gillespies Beach. Keep your mosquito repellent handy here because the sandflies are everywhere and they leave you with a nasty itch.