La Défense was one of the regions in Paris that we wanted to visit. We spared half a day to see this business district. The most iconic architecture of this region is Grande Arche which was completed in 1989. It looks like a big cube and is aligned with Arc de Triomphe and Arc de Triomphe du Carrousel in front of the Louvre.
The stairs of Grande Arche were full of people that were eating lunch or enjoying the view. We hung around there until we got back to the city center for a boat tour on the Seine.
I definitely recommend the boat tour on the Seine if you are visiting Paris for the first time. It helps you to see many places at once and decide where to focus later on.
The tour finished somewhere close to the Eiffel Tower, but since we had our pre-booked tickets for the tower for tomorrow, we kept walking in the St. Germain district.