Belle Epoque (literally "the Beautiful Age") is the name given to the period between 1871, when the Franco-Prussian war ended, and 1914, when the First World War began. Once France was forced to endure the wars and hardships of the 20th Century, it was nostalgically thought of as a golden age, both prosperous and peaceful.*
* A better name for it would have been the If Only They Knew What Was Coming Époque.
Paris, already referred to as the City of Light, grew in size and economic power thanks to technological advances. The Parisian quality of life improved as well.*
* And they didn't even have social networking then.
Come to think of it, maybe it was a good time to be alive after all. Yeah?
The 1889 World's Fair exemplified the spirit of the times, and marked the construction of the Eiffel Tower, a symbol of France's new engineering prowess and of the Belle Époque itself. Just as iconic is the Paris Metro, whose construction began in 1898 and which opened to the public two years later.
However, these weren't the first grand accomplishments of the era. The Statue of Liberty was built over a decade earlier as a gift to the United States, representing the Roman goddess of freedom and celebrating American independence.
But while Paris became the cultural capital of the world, and its arts and literature flourished, there was also political and racial tension. Anarchist groups* who saw nothing but bourgeois decadence in the culture of cafes and cabarets (such as the Moulin Rouge) resorted to acts of terrorism.
Soon, a more widespread terror would put an end to this golden age, as war once again gripped the continent.