River cruising: the Vikings are coming - in their 21st-century longships It is on the majestic Rhine and the "blue" Danube that the Viking longships Odin, Idun, Freya and Njord will be sailing - although so high is demand that they are almost fully booked in the main summer season. On board Odin I'm in good company: Joanna Lumley, who has been chosen as the ship's "godmother" (each vessel has its own), is there to smash open the bottle of champagne at the launch. What is immediately striking about the longship is its layout: the Norwegian designers, Petter Yran and Bjorn Storbraaten, have made it a priority to give passengers as much light, sense of space and access to fresh air as possible. In the two-deck atrium, a display of live moss and flowers on the lower level is set against a curved glass stairway, while upstairs are a small library and two computers for guests. Electric doors open on to exterior stairways leading to the sun deck above, which has a giant chess set, a golf-putting area, shuffleboard, solar panels and a little herb garden. Like other Viking ships I know, these newcomers are clean, tidy and free of clutter. Though Odin's beam is just 37ft - the maximum permitted in the Rhine and Danube locks - her rounded bows allow room for a splendid terrace, the Aquavit, which forms part of an indoor-outdoor lounge with retractable glass doors, where you can eat, drink or simply relish the view - in my case, the twinkling lights of night-time Amsterdam. The most spacious of the 95 cabins are two 440 sq ft "Explorer" suites, which have a wraparound balcony with a 270-degree view, a living area with sofa, chairs and table and a bedroom. Although they sit at the stern, there is little noise or vibration, even at full speed - thanks to the hybrid diesel-electric propulsion system which, as well as being energy-efficient, is quiet. Three quarters of cabins have a balcony, whether full or French-style (with glass doors and just enough space outside to put your toes); only the 150 sq ft "Standard Staterooms" have just a window. The full balconies, however, take a little space away from the bathrooms, which, to say the least, are compact. All rooms feature down bedding, bathrobes and slippers, bottled water replenished daily, a fridge, a sophisticated television and entertainment system, movable bedside lights, good under-bed luggage storage, plenty of "soft-close" drawer space, an illuminated wardrobe with sliding doors, a safe, a satellite phone and audio sets for shore excursions. Bathrooms have opaque-glass sliding doors, heated flooring and L'Occitane toiletries. The rooms are arranged sensibly and decorated in restful beiges, browns, blues and greys, with cherrywood cabinetry and soft lighting - but soundproofing could be better. The longships do most of their mileage at night, mooring up by day so passengers can explore. Their routes take in medieval towns such as Miltenberg, which has Germany's oldest inn, sights such as Bamberg Cathedral and cities such as Vienna and Bratislava. Unlike many ocean cruises, river cruises are all about visiting places en route, so other "entertainment" is minimal - there might be early-morning stretching on deck, classes in regional cookery or crafts, or small-scale classical or folk performances related to the local area. Also given a local slant on the longships is the food - Viking has upgraded its menus lately, in quality and choice. You can eat in the sleek main restaurant, with floor-to-ceiling windows, crisp white tablecloths and a five-course evening menu, or there's lighter fare on the Aquavit Terrace. Beer, house wine and soft drinks are included during lunch and dinner. The staff are professional and attentive - and drawn from the firm's 1,800 employees around the world rather than from agencies. My favourite part, however, is the ride itself - smooth and almost silent. And I like the idea that the Norse gods are riding with me, perhaps doing a river dance. An eight-day Romantic Danube cruise, from Nuremberg to Budapest or vice versa, costs from £1,895 in November, £1,595 in December and £1,395 in May 2013, including full board, drinks, six tours, port charges and return flight from airports in Britain (020 8780 7995; vikingrivercruises.co.uk). River cruising for beginners Rivers lead you into the heart of a country, and to fascinating destinations that can't be reached by ocean-going ships. For the countries through which they run, they are an economic lifeline. For the holidaymaker, they can offer peace, romance or adventure (without the danger that many associate with the open sea). River ships provide an antidote to large, ocean-going cruise liners. They are all about lazy afternoons spent on "rivertime" - aboard anything from a waterbus to a floating palace - and they really do glide rather than sail. River ships run to no more than four decks - thanks, in part, to the restrictions placed on a vessel's dimensions by locks and bridges. Almost all are built on a monohull arrangement. Because of their long, "low-slung" design, public space may be limited to a restaurant and a main lounge. On board, you're unlikely to find casinos, bingo, cabaret or art auctions. When your ship docks, you simply walk off it (or across several neighbouring ships when they are tied up together in busy places such as Budapest). I've never come across a queue to get into town while on a river cruise, and when the ship is moored you can come and go as you please. During evenings and early mornings it can get chilly when the vessel is moving, even in hot climates. Take a windproof, plus trousers, a hat and comfortable shoes for wearing on deck and shore excursions (avoid heels: many older European cities and towns have cobblestone streets). The dress code in the evening, whether aboard or on land (some itineraries include overnight stops), may be a little smarter than by day.