In its colonial heyday Dakar was one of the major cities of the French Empire, comparable to Hanoi or Beirut. French trading firms established branch offices there and industrial investments (mills, breweries, refineries, canneries) were attracted by its port and rail facilities. It was also strategically important to France, which maintained an important naval base and coaling station in its harbor and which integrated it into its earliest air force and airmail circuits, most notably with the legendary Mermoz airfield (no longer extant).