Possible Clues:

• Venus de Milo's home
• Museum that's normally closed during the winter?
• World's most-visited museum
• Museum in central Paris
• Stories about radiation detected in Parisian building
• Volunteers dropped, sent to a foreign art museum
• World's most-visited art museum
• Paris museum; slat
• Roof turret allowing smoke to escape from a medieval building; a famous museum
• Horizontal overlapping slat in a door and art gallery