Book early for discounts on Viking next year.

One of the fastest-growing segments of the travel industry in the past decade has been river cruises, and a leading specialist is offering big discounts until July 31 on 2011 sailings.

Viking River Cruises, which sails in Europe, Russia, China and Egypt, is offering two-for-one cruises plus up to two-for-one pricing on round-trip international air.

Plus, the deal includes wine with all dinners. The Viking Prestige will sail the eight-day Romantic Danube itinerary from Budapest to Nuremberg. Viking Emerald (a new ship launching next year) sails China’s Yangtze River.