What are cabins like?

Standard cabins on ships built in the 1980s can be as small as 90 square feet, while the average room on many new boats is 200 square feet. Nearly all lines offer only outside cabins, so you can expect a window and a view. The cheapest rooms are just above water level, where the scenery isn't as good. Riverboats are narrow, so they rarely have room to provide balconies. It's standard for cabins to come with a hair dryer, air-conditioning, and TV.

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When should I go?

The peak seasons are late spring and early fall, when temperatures are neither too hot nor too cold. You'll find the cheapest prices during the iffy periods of early spring and late autumn, and some lines have discounts during the hottest weeks of July and August. (The savings might be negated because that's when airfare costs the most.) Many passengers plan their cruises according to the agricultural cycle. "If you're interested in wine, you may want to go when the grapes are being harvested in the fall," says author Linde. "And if you want to see tulips in Holland, go in April."

How much?

It depends on the cruise line and the season. Avalon, a middle-of-the-pack line, has a seven-night "Tulip Time" cruise through Holland and Belgium starting at $1,600 per person. Viking, which offers a similar level of luxury, lists promotions on its website, sometimes bringing rates down to less than $1,000 for a week. Grand Circle Travel, a general tour operator that markets to Americans 50 and older, offers nine different river cruises in Europe, sometimes for as little as $1,000 with airfare from New York. The international clientele of Sea Cloud Cruises are used to paying over $3,000 a week for outstanding food, sophisticated atmosphere, and huge cabins with marble floors in the bathrooms.

What costs extra?

The cruise price covers three meals per day, and oftentimes afternoon tea, wine at dinner, and guided excursions. Tips are not included. There'll be an envelope in your cabin for gratuities; the standard is for each passenger to leave around $10 per day--preferably in the local currency.