-- Summer's not quite over: Until Sept. 30, receive a free fourth night, plus other perks, with the Summer Escape promotion at the Waldorf Astoria Collection and Conrad Hotels and Resorts. The deal covers 20 properties around the country, including Puerto Rico. For example, at the Arizona Biltmore Resort and Spa in Phoenix, receive a free fourth night, $25 credit for every $100 spent on-site, free breakfast for up to two children younger than 12 and 30 percent off spa and salon treatments. Nightly rate starts at $199, plus $28 daily resort fee and 12.27 percent tax. For the Conrad Miami, receive $50 food and beverage credit per two-night stay on top of the gratis night. Rate from $139, plus 13 percent tax. Info: 888-214-1592, www.hiltonluxury.com/escape. Mention code PRESIN. -- Viking River Cruises is offering two-for-one rates on five holiday voyages in Europe, including three new itineraries. For example, the eight-day Christmas on the Rhine cruise travels round trip from Cologne, Germany, and starts at $1,456 per person double for a Category D cabin; original price was $2,799. Port charges, shore excursions and all meals included. The trip aboard the Viking Helvetia stops at Christmas markets in Strasbourg and Baden-Baden, Alsace wine country, the Mainz Christmas fair and more. Depart Nov. 30 or Dec. 7 or 14. The twofer also applies to these new offerings: Danube and Prague Discovery (four-night cruise in Germany's Bavarian region and three nights in Prague; from $1,532) and Holiday in the Rhineland (nine-day cruise from Amsterdam to Cologne; from $1,214). Book and pay in full by Sept. 30. Request code 61W. Info: 800-304-9616, www.vikingrivercruises.com. (Begin optional trim) -- South African Airlines is offering a six-night Cape Town in Style trip starting at $2,219 per person double. Price includes four nights' lodging in Cape Town and two nights in Stellenbosch, six breakfasts and two dinners, round-trip airfare from Dulles to Cape Town, ground transportation, taxes and fees. Travel by Dec. 15. Booked separately, airfare and hotels alone would cost at least $2,223 per person double. Info: 888-722-4872, www.flysaavacations.com. (End optional trim) Prices were verified and available on Thursday afternoon when the Travel section went to press. However, deals sell out quickly and are not guaranteed to be available. Restrictions such as day of travel, blackout dates and advance-purchase requirements sometimes apply. 