We have been to Ushuaia twice, both times on cruise ships.   It is a very interesting place and is billed as the southernmost city in the world.  Technically there is a small city in Chile that has that honor, but who’s counting.    We were there in January, which is the middle of their summer and both times the weather was only in the 60’s.    In their winter it is a major ski area and a lot of Olympic teams train there.   The national park just to the south of Ushuaia is also the end of the Pan American highway system that runs all the way to Alaska.   It is a dirt road at the end point. 

Ushuaia is the jumping off point for many of the small ship excursions (expensive) to Antarctica.  These are usually 7 day round trips. 

Cruise ships, either before or after visiting Ushuaia, go to Cape Horn and sail around the island.  Both times we went the seas were calm but the area is famous for rough seas at times. We also got to see some really close up views of Glaciers as we left the Beagle Channel.