Lupin III: Princess of the Breeze - Kakusareta Kuuchuu Toshi

The story takes place in Shahalta, a small European city-state suspended in the air. The city's government is currently in the process of transitioning from a monarchy to a republic, and as part of the celebration, a national treasure exhibition is being held. Lupin III tries to infiltrate the exhibition to obtain the secret royal treasures before they can be secured, but the sky pirates beat him to it.