Paris was at the front of the war effort during the First World War.
They decided to resist and to create a Parisian "Commune" government.
The result was a bloody Semaine Sanglante Around 20,000 "communards" (resistants from the communes government) were executed before May 28th 1871, when the fighting ended.
German General von Choltitz did not destroy all Parisian monuments even though Adolf Hitler asked him to (Hitler visited the city in 1940). The business district, La Défense, started at this time.
The RER (a subway network), was built to complement the Métro. Many motorways were built in the suburbs, such as the Paris Périphérique.
Overall, the city is relatively flat, and the lowest elevation is 35 m (115 ft) above sea level.
Paris has several prominent hills, of which the highest is Montmartre at 130 m (427 ft). The city's last major annexation of outlying territories in 1860 not only gave it its modern form but created the twenty clockwise-spiralling arrondissements (municipal boroughs). Paris has an oceanic climate (Köppen climate classification Cfb) and is affected by the North Atlantic Current, so the city rarely sees extremely high or low temperatures, such as the heat wave of 2003 and the cold wave of 2006.The Baron Haussmann's earlier renovations helped the army a lot.Paris hosted two Universal Expositions at the end of the nineteenth century.Central Paris wasn't bombed much during World War II.There were no strategic targets for Allied bombers. Many large social estates (or cités, in French) were built.In 2008, president Sarkozy launched an international urban and architectural competition for the future development of Paris.