Parisian hotels tend toward the stylish side of things just by virtue of their environment, but even here there are outliers. The ultra-chic Château Voltaire is named not for the Enlightenment philosopher but for the fashion brand Zadig & Voltaire, for which hotelier Thierry Gillier is better known. For this venture, Mr. Gillier enlisted creative director Franck Durand and the Parisian architecture studio Festen to translate his aesthetic into a hospitality language, and the resulting hotel is every bit as stylish as its star-studded genealogy would suggest. The accommodations are perhaps surprisingly low-key, with a subtlety and sophistication that’s unusual even in Paris; on the other hand, the bar, La Coquille d’Or, is dark and moody in leather and velvet. Somewhere in the middle is the hotel’s ultra-chic Brasserie l’Emil, which serves fine and simple fare to a crowd of in-the-know locals. All this for a hotel of just 32 rooms and suites — plus a subterranean wellness center containing a sauna and a plunge pool. The penthouse apartment also comes with an outdoor terrace with landscaping by Louis Benech, and does double duty as a highly photogenic events space.