6. Centre Pompidou
Three decades into its life, it's clear that the Centre Pompidou has succeeded in its aim of being both art gallery and cultural hub. Its modern and contemporary art collection, with over 50,000 works and multiple temporary exhibitions, is one of Europe's most significant, and its public library and performance spaces throng with life — more than 6 million visit the Pompidou each year. The landmark building, designed by Richard Rogers and Renzo Piano, wears its skeleton on the outside, with tubes and structures color-coded to denote their function — blue for air conditioning, green for plumbing, yellow for electricity, red for elevators. (Piano, who championed the revitalization of the Pompidou's environs, has his workshop a stone's throw away in the Marais.)