The hub of transportation in Lausanne is Lausanne-Flon, Bel-Air, St-François :
Lausanne-Flon, Bel-Air, and St-François are all located in a less than ten minute walking distance from each other.
Nearly every bus line in Lausanne passes through Bel-Air in two directions, St-François is a termination point for buses, that run from the center of Lausanne to their other terminations far from the center in many convenient directions.
Lausanne-Flon is the main point where the métro (M1 and M2) underground/subway lines and many TL buses meet. It is also where the LEB (regional train to Echallens, northern Vaud district) main station is located.
All of the best shopping, dining, and night-life in Lausanne are located near these places, as well. You will find it as no surprise that some very thoughtful city planning has made these three places the hub of the city’s transportation system.