Europe’s great cities tend to have an abundance of fine hotels, but occasionally, a new property comes along that promises to raise the bar to a different level. The 93-room Waldorf Astoria Amsterdam opened on May 7 in an ideal location on the Herengracht — the “Gentlemen’s Canal” — a 15-minute walk from the Museumplein. Six magnificent 17th- and 18th-century houses (two of them former mayoral residences) have been combined to create a single building. Among the hotel’s many attributes are the city’s largest private garden (with 5,000 tulips), a restaurant by three-star chef Sidney Schutte, an indoor pool and a Guerlain spa.