GETTING THERE: Cologne has a major international airport, which it shares with Bonn, and the city is where Lufthansa German Airlines has its headquarters. From Du sseldorf airport, which now has a larger traffic volume, it is a one-hour train trip to the center of Cologne. From Frankfurt (120 miles) it is about 1 1/2 to two hours by train, using either Inter-City expresses, which leave from the main station, or the four-times daily Lufthansa-operated "Airport Express," which leaves from the Frankfurt Airport terminal building's subterranean platform. From Bonn (15 miles) it is a 20-minute train, half-hour car, or one-hour streetcar ride. From Brussels or Amsterdam, figure three hours by train or car.

Cologne's railway station, right between the Rhine and the cathedral, is one of the largest in the country and is serviced by nearly 1,000 Inter-City express trains from and to all major points in West Germany, the Netherlands, Belgium and France.

The Rhine, besides being a good starting point for cruises, is also a traffic artery. Ko ln-Du sseldorfer Rheinschiffahrt A.G. operates steamers and hydrofoil boats between Mainz and Cologne, with stops in Bingen, Koblenz and Bonn, up to four times daily in the peak summer months, three times daily in the spring and fall.

GETTING AROUND: To see Cologne properly, it is best to walk, but the public transit system -- underground and surface streetcars -- is excellent. A single ticket is DM 2.20 (about 70 cents), a 24-hour ticket is DM 6 ($2). Tickets can be obtained from the automats at station stops and must be validated by sticking them into the meters aboard vehicles.

ARRANGEMENTS: City tours, sightseeing, English-speaking guides, tours of the Romanesque churches, cathedral, major museums and other important sights, as well as out-of-town and Rhine river excursions, can be arranged and booked with the Verkehrsamt, the Tourist Office, at No. 19 Unter Fettenhennen (directly across from the main portal of the cathedral), D-5000 Cologne 1, telephone (221 from abroad, 0221 from within Germany) 221-3332, 221-3388, 221-3340 or 221-3345 (which answers weekdays from 8 a.m. to 9 p.m. and Sundays and holidays from 9:30 a.m. until 7 p.m.)

MUSEUMS: The Roman-Germanic Museum is open daily except Mondays from 10 a.m. to 5 p.m. and Wednesdays and Thursdays until 8 p.m. Admission is DM 3 ($1).

Museum Ludwig (presently at An der Rechtschule, due to move to its new $100 million complex behind the Roman-Germanic Museum late this year or early next year) is open daily except Mondays from 10 a.m. to 5 p.m. and Tuesday and Thursdays until 8 p.m. Admission is DM 3.

Wallraf-Richartz Museum (same location as Museum Ludwig and due to move with it), containing 13th- through 19th-century painting and 18th- and 19th-century sculpture, is open daily except Mondays from 10 a.m. to 5 p.m., Tuesdays and Thursdays until 8 p.m. Admission is DM 3.

The Schnu tgen Museum in St. Cecilia's, 29 Ca cilien Strasse (Neumarkt subway and streetcar stop), is open daily except Mondays from 10 a.m. to 5 p.m. and until 8 p.m. on the first Wednesday of each month. Admission is DM 2.

CHURCHES: The Dom, the cathedral, is open from early morning until dusk, though never after 7:30 p.m. Admission is free. The cathedral's treasury is open from 9 a.m. to 5 p.m. weekdays, and from 1 p.m. to 5 p.m. Sundays. Admission is DM 2 . Guided tours of the cathedral museum can be arranged through the Verkehrsamt and rates in English are DM 40 (about $13) for the first hour and DM 15 for each additional hour, for groups of up to 25 persons.

The Romanesque churches have different hours, and some are closed during the long lunch period.

Those open all day are St. Andreas, at Andreaskloster; St. Georg's, Georgsplatz No. 1; St. Kunibert, No. 6 Kunibertkloster; St. Maria in Lyskirchen, No. 6 An Lyskirchen; Gross St. Martin, No. 8 Martinspfo rtchen; and St. Pantaleon, No. 6 Am Pantaleonsberg. The others -- St. Aposteln, No. 10 Apostelnkloster; St. Gereon, No. 4 Gereonshof; St. Maria im Kapitol, No. 6 Kasino Strasse; St. Severin, Severinskirch Platz; and St. Ursula's, No. 30 Ursulaplatz -- generally close their doors at noon and reopen between 2 and 3 p.m., depending on the mood of the sexton.

WHERE TO STAY: The best hotels close to the cathedral and railway station and within easy walking distance of the most important sights are:

Excelsior, Trankgasse No. 1-5, D-5000 Cologne, phone (0221 from within Germany or 221 from abroad) 2701; 65 singles to $75, 61 doubles to $110.

Dom Hotel, Domkloster No. 2a, D-5000 Cologne, phone 233751; 70 singles to $70, 56 doubles to $110.

Senates Hotel, Unter Goldschmied No. 9-17, D-5000 Cologne, phone 233861; 32 singles to $50, 15 doubles to $70.

Hotel Ko nigshof, Richartz Strasse 14-16, D-5000 Cologne, phone 234583; 45 singles to $55, 50 doubles to $95.

Am Augustinerplatz Hotel, Hohe Strasse 30, D-5000 Cologne, phone 236717; 24 singles to $45, 32 doubles to $70.

The Verkehrsamt also makes hotel reservations and can advise on more moderate accommodations in pensions and private homes.

DINING: The quaintest, most colorful Ko lsch pubs, where two beers and a solid two- or three-course lunch will cost no more than $5 per person, are:

Bei der Tant, Ca cilien Strasse No. 28 (across from Schnu tgen Museum), phone 219720.

Hofbra u Fru h, Am Hof No. 12-14, 212621.

Brauerei zur Malzmu hle, Heumarkt No. 6, 210117.

Brauhaus Sion, Unter Taschenmacher No. 5-7, 214203.

For moderately priced German and Cologne food in rustic, pleasant surroundings, try:

Alt Ko ln, Trankgasse No. 7-9 (near the cathedral and railway station), 134471.

Weinhaus im Walfisch, Salzgasse No. 13, 219575.

The top culinary spots with dinner for two around $75-$100 are:

Goldener Pflug, Olpener Strasse No. 421 in Cologne-Merheim, 895509, reservations essential.

La Poele d'or im Weinhaus Wolff, Komo dienstrasse No. 52, 134100, reservations recommended.

Chez Alex, Mu hlengasse No. 1, 230560.

Bei Rino-Fontana di Trevi, Ebertplatz No. 3, 721108.