European river cruising has been the quietly booming corner of luxury travel for the past three years. While ocean lines fight for share with mega-ships, a handful of operators have built smaller boats that thread through Vienna, Bordeaux and Porto with all-inclusive service that competes with five-star hotels. The trade-off is that supply has not kept up with demand. Premium suites on the Rhine and Danube routinely sell out twelve to eighteen months ahead, and 2026 is already constrained on peak summer dates. This guide covers the three operators that matter at the top of the market, the four routes [...]