Ushuaia is considered to be the southernmost city on earth and also says about itself to be located at the end of the world. The Chilean Puerto Williams by the way, is located even more south, but with just over 2000 inhabitants, however, rather a village.
In Ushuaia not only airplanes arrive, but also various cruise ships. Ushuaia is also the starting point for many Antarctic trips. If you are thinking about doing a trip to Antarctica, I hope you don’t have to care about money. On the spot I saw a last minute offer of 5000 USD (11 days trip). But for Last Minute you have to bring time and flexibility. Regularly it is even more expensive. Have I been to Antarctica? No, unfortunately I do not have a cash cow yet.
What else can you do in Ushuaia? There are boat trips to penguins and sea lions and along the lighthouse. Since I had already seen more than enough penguins and sea lions in Punta Tombo and on Peninsula Valdes shortly before and only had 2 full days in Ushuaia, I decided not to do the boat tour.
In the National Park Tierra del Fuego there is the End of the World train. Alternatively you can do several hiking trails in the park. More on the detail page.
There are also several trekkings in the surroundings of Ushuaia but outside the park. For these you don’t need to the park entrance fee. You can e.g. hike to a glacier or to one of the lagoons. I have been to Laguna Esmeralda and have described the trail in more detail.
Ushuaia is also famous for its king crab. In several restaurants there are water basins where you can see the crabs still swimming in them. You can get a whole king crab, indicated that this dish is for 2 persons. I was thinking about taking a whole crab anyway. But as I know that I am too stupid to open the crab properly, I decided to have a crab soup and a normal dish for 1 person with king crab. It was very tasty. As a dish it is certainly one of the more expensive in Argentina. Compared to what you would pay in for king crab in many other parts of the world, it is super cheap.