When in Ushuaia, the most southern city in the world and here, taking a boat trip to Beagle Channel is your number one priority.
To give you a bit of a background, the English founded Ushuaia at the end of 19th century when the British ship HMS Beagle was exploring Tierra del Fuego. They reached the channel in 1833, which is actually a navigable strait between the Pacific and Atlantic, together with two other famous passages: Magellan to the north, and Drake to the south.
So they decided to name the channel after the ship. Onboard the ship there was a young and promising amateur naturalist named Charles Darwin, who was of course so thrilled to find such a wide variety of birds, penguins and sea lions.