When my mom first came to Paris, we were in the Marais and as we walked past the Hôtel de Ville, I pointed it out to her and she said, "Wow, I wish we were staying in THAT hotel!"
Easy mistake, but it's not, of course, a hotel at all... the "hôtel de ville" of any French town is the city center or town hall. It's where you go to sort out administrative woes and pick up brochures for what's happening around town. But Paris takes the concept much further and its Hôtel de Ville goes way beyond its definition as a city center. This magnificent structure has been around since the 1357 and is so much more than "the city's local administration" (as Wikipedia has described it).