This is a view to Montmartre from the top of the Arc de Triomphe and it gives a good view of the “Boulevards” of Paris. Now the Champs-Élysées is the ubiquitous shopping street (although personally I feel it lost its charms many decades ago.) and gives little indication of the original intention of the “Boulevards” which cut a swath through pre-Haussmann Paris.
The new Paris of Napoleon the Third was built at a time when the French monarchy had an unfortunate history of being removed. Consequently Paris as we know it today with its grand boulevards is largely shaped on these wide thoroughfares which were constructed to allow the rapid movement of heavy weaponry around Paris in case of a threat from outside or within. The medieval labyrinth of old Paris made it impossible to respond rapidly to unrest and gave the rebellious elements endless escape routes and hiding places. The boulevards swept away all of this and allowed unprecedented access to the whole of central Paris.
The French word “boulevard” originally referred to the flat top of a rampart which surrounded a fortress and the term was adopted to refer to these wide military access ways when Paris was remodeled in the mid to late 19th Century.