Paris, the capital of France, earned the nickname 'La Ville Lumière' (The City of Light) both because of its fame as a center of ideas during the Enlightenment and because it was one of the first cities to adopt gas street lighting. The city’s urban design was radically transformed in the mid-19th century by Baron Haussmann, who replaced cramped medieval alleys with wide boulevards and uniform limestone buildings. A key feature of Paris is the 'Axe Historique' (Historical Axis), a line of monuments and grand thoroughfares that extends from the Louvre, through the Tuileries Garden and the Champs-Élysées, to the Arc de Triomphe and the modern Grande Arche de la Défense. Paris is divided into 20 administrative districts called arrondissements, which spiral outward like a snail shell (escargot). As a global center for gastronomy, fashion, and art, it remains the most visited city in the world, with the Eiffel Tower standing as its most recognized symbol despite being originally intended as a temporary structure for the 1889 World's Fair.