Columbus, the pleasantly folksy capital of Ohio, claims to be the largest city in the world bearing the name of the famous mariner -- which explains why it is organizing what is expected to be the nation's premier tribute to Christopher Columbus on the 500th anniversary of his first voyage to the New World. The six-month-long extravaganza, called AmeriFlora '92, may be the next best thing to a world's fair.

The official World's Fair next year is being held, of course, in Seville, Spain, but Columbus's mini-version should do quite nicely, thank you, for travelers unwilling to make the expensive transatlantic trip. Occupying an 88-acre city park two miles east of downtown Columbus, the $95-million exposition will combine an international flower show, an offbeat cultural festival and an exotic food fair -- and much more -- in one big gala beginning April 20 and concluding Oct. 12. The theme is "Columbus-92: A World to Discover."

Elsewhere in the country, at least 21 cities on the Atlantic, Gulf and Pacific coasts -- including Baltimore, Annapolis and Norfolk -- are preparing to welcome the Nina, the Pinta and the Santa Maria, the Spanish-built replicas of Columbus's fleet of tiny caravels, which first spied land in the New World on Oct. 12, 1492. Already en route, the latter-day vessels are scheduled to dock first on Feb. 14 (weather permitting) in Miami, where they will be escorted into the harbor by a parade of 10,000 sail and power boats.

The many U.S. events commemorating Columbus's voyage are as diverse as the nation and include major museum exhibits, Tall Ship rallies, historical symposiums, new Spanish-heritage statuary, classical concerts, art shows, athletic events, dance performances and giant parades. A number of national parks are planning special visitor center exhibits reflecting on Spanish exploration and colonization. These events will be taking place from now through the end of 1992 and even into 1993.

In addition to Columbus and Miami, major commemorative programs are planned in New York, Boston, Philadelphia, Memphis, San Francisco and Corpus Christi, Tex., which will erect a new, nine-foot-tall statue of Columbus next year. In Washington, the Smithsonian Institution has taken the lead with a series of special Columbus exhibits, one of which, "Seeds of Change," already has opened. And the East Building of the National Gallery of Art is displaying an exhibit of 600 artworks from the Columbus era, although this exhibit, "Circa 1492," closes Jan. 12.

Some of the nation's commemorative events honor Spain, whose monarchs, Isabella and Ferdinand, financed Columbus's voyages and won an empire, and others focus on Italy, the country of his birth. An official state-by-state calendar of Columbus-related happenings in the United States is being compiled on computer by the congressionally created Christopher Columbus Quincentenary Jubilee Commission in Washington. Already there are so many items are listed it takes more than nine hours to print out a full copy of the calendar.

One of the most unique projects -- and one that may have lasting significance -- is scheduled to take place in western Maryland, where state quincentennial officials are planning a Native American "summit" and cultural festival in mid-October. Representatives of Indian tribes throughout the country are being invited to gather for an in-depth discussion of the needs and goals on the American Indian population in the 21st century. The summit, to be held at Hagerstown Junior College, will be followed by traditional dances, a cook-out and other festivities at nearby Fort Frederick State Park on the Potomac River.

Christopher Columbus is a less-than-heroic figure to many Indians, who argue that his voyages brought disease, slavery and death to their ancestors, and they reportedly are not enthusiastic about celebrating the quincentennial. But the summit apparently is an idea that is finding favor among the tribes, according to Stan Heuisler, who heads Maryland 1992, the state's commission for the quincentennial. "This is a novel approach," he says, "and people are getting excited."

Many of the quincentennial events are still months away, and in many cases planning is still tentative and subject to change. Nor has all the necessary financing been arranged. But based on current information, these are among the most significant Columbus festivities scheduled for the months ahead:

America's Fair On New Year's Day, TV viewers will get a preview of AmeriFlora '92, Columbus, Ohio's impressive commemorative project. As befitting a fair that begins with an international floral exposition, it has entered a large, flower-bedecked float in the annual Tournament of Roses Parade in Pasadena, Calif.

Flowers are only one aspect of the fair, but an important one. The international floral show will run for only two weeks, beginning on opening day, April 20. But at least 12 nations are installing traditional gardens that also will be on display until the fair closes Oct. 12. Japan, for example, will create a tea garden, and Russia is planting a typical country garden that might be found adorning a summer dacha. And 20 of this country's most novel gardening ideas -- among them a water garden -- will be created in a sprawling exhibit called "America's Backyard."

A major presentation will be "Seeds of Change," a spin-off of the exhibit at the Smithsonian Institution's National Museum of Natural History that traces the impact of Columbus's voyages on both the old and the new worlds. At AmeriFlora, the focus will be on how the Midwest was affected. It opens May 31. In addition, General Motors, which has created a wide-screen film presentation for the U.S. pavilion at Expo '92 in Seville, will show the same feature at AmeriFlora.

Exotic foods will tempt at the "Taste of Nations" food court; jugglers, magicians, clowns and other street performers will roam the entire fair site; and stage entertainment will be provided by marching bands, choirs, jazz ensembles, orchestras, dance troupes, drill teams and other groups from throughout the country. With so many bands on tap, a parade is scheduled every day of the fair.

But maybe the most intriguing attraction, for youngsters only, is the "Dino Discovery Dig." On daily digs, budding scientists will be turned loose on a giant sandpile where the fossil remains (re-created in plastic) of a 70-foot-long brontosaurus are buried. As the youngsters uncover the pieces, they can assemble them into a complete dinosaur skeleton. Daily admission to AmeriFlora is $19.95 for adults and $9.95 for children ages 4 to 12.

A full-size replica of the Santa Maria, Columbus's flagship, is being built as part of the city's celebration, and it is anchored on the Scioto River in downtown Columbus. Ninety-eight feet in length, the Santa Maria is a three-masted, square-rigged nao, typical of a merchant cargo ship in the 15th century. It will be completed and open for tours led by costumed interpreters beginning in April.

Ports of Call Using historical documents as a guide, Spain has invested more than $15 million in building replicas of Columbus's three caravels, the Nina, the Pinta and the Santa Maria, and launching them on a new voyage to the New World in Columbus's path. The small vessels are as nearly authentic as possible, based on current research. For example, the same type of wood and other materials in common use for shipbuilding in Spain in the 15th century were incorporated in the replicas, and the nails were hand-forged using nails recovered from an old shipwreck as a model.

Christened in October 1990, the trio of ships called on Mediterranean and Atlantic ports for a year and drew huge crowds. On Oct. 13 of this year, they set sail for the Western Hemisphere from the port of Huelva near Palos de la Frontera, where Columbus launched his initial voyage. The fleet carries a total crew of 62 (28 on the Santa Maria and 17 each on the Nina and the Pinta), the members of which are Spanish navy officers and selected volunteers. En route to this country, the ships stopped in the Canary Islands, as Columbus did, and are scheduled to spend New Year's Day in San Juan, Puerto Rico.

Sailing under their own power, the ships carry the same type of navigational equipment Columbus used, and they are as spartanly furnished. The Nina and the Pinta carry only a rustic pine table, a few stools and the personal chest of each crew member, most of whom must sleep on deck wherever they can find a protected spot. The fleet flies the ancient flag and standard of Castile and Leon, the realms of Isabella and Ferdinand.

While in port, the ships will be open to visitors. The U.S. itinerary has been arranged by the Spain '92 Foundation, a Washington-based organization established by Spain to develop cultural and educational programs in this country related to the quincentennial. Spain '92 also has built a float for the Rose Parade on New Year's Day.

Weather permitting, the caravels will call at the following U.S. ports: Miami, Feb. 14 to March 1; Corpus Christi, March 13 to 22; Galveston, Texas, March 25 to 29; New Orleans, April 3 to 5; Tampa, Fla., April 10 to 19; St. Augustine, Fla., April 25 to 27; Charleston, S.C., May 1 to 3; Norfolk, May 8 to 10; Baltimore, May 15 to 25; Annapolis, May 27 to 29; Philadelphia, June 6 to 14; Wilmington, Del., June 16 to 17; Atlantic City, June 19 to 21; New York, June 26 to July 19; New London and Mystic, Conn., July 24 to 26; and Boston, July 31 to Aug. 16.

From there, the vessels will be transported via the Panama Canal to the West Coast, according to David Nowland, a spokesman for the Spain '92 Foundation. The fleet will then resume its voyage, docking in San Francisco from Oct. 2 to 25; San Luis Obispo, Calif., Oct. 30 to Nov. 1; Los Angeles, Nov. 6 to 29; San Juan Capistrano, Calif., Dec. 4 to 6; and San Diego, Dec. 11 to 20. Eventually, the ships will be placed on permanent exhibit in the United States at a place yet to be determined.

City Celebrations Among the cities planning major quincentennial programs:

Philadelphia: A year-long celebration under the title "Neighbors in the New World" culminates in a giant parade Sunday, Oct. 11 (Columbus Day weekend), led by Grand Marshal Luciano Pavarotti, the opera star. Earlier, the Philadelphia Flower Show, March 8 to 15, will feature a garden and courtyard from the Spanish-influenced American Southwest. And throughout next year, the Franklin Institute Science Museum is featuring an exhibit on navigational tools and ship artifacts.

New York: The big weekend here is the Fourth of July, when the three Columbus caravels are in town. The city will play host also to a gathering of Tall Ships. A major fireworks display and an outdoor concert are being planned.

Memphis: Each year, the Memphis in May International Festival honors a different foreign country. In 1992, the country is Italy. Throughout the month, more than 100 events or exhibits are scheduled, including a show of Italian paintings, another of Etruscan artifacts, an Italian wine- and food-tasting festival and a "Viva Italia" pops concert on May 2.

Miami: On Feb. 14, the arrival of the Columbus caravels will be celebrated with a parade of 10,000 pleasure craft. Other Spanish heritage programs, including concerts and seminars, are being planned throughout the year.

San Francisco: The caravels will be in San Francisco during the Columbus Day weekend, Oct. 10 to 12, and the city is taking advantage of their presence with a gala nautical celebration. There will be an international naval review featuring modern naval vessels, a Tall Ships rally, the largest fireworks display ever on the West Coast and a reenactment of the landing of Columbus.

The Smithsonian

In Washington, the Smithsonian Institution is presenting a series of scholarly exhibits reflecting on the impact of the Columbus voyage. Among them:

"Seeds of Change," National Museum of Natural History: Artifacts from Europe, the Caribbean and South America trace the impact of five so-called "seeds" -- corn, potatoes, horses, sugar and disease -- and how they changed both the old and the new worlds. Through April 1, 1993.

"American Encounters," National Museum of American History. A look at the American Southwest, a mingling of Indians, Hispanics, African Americans and Anglo-Americans who settled in New Mexico's Upper Rio Grande Valley. Opens June 24.

"Where Next, Columbus?," National Air and Space Museum: While historians examine the past 500 years, the museum peers five centuries into the future, reflecting on the scientific, technological, economic, ethical and political issues of space travel. Opens in December 1992.

For Information

Christopher Columbus Quincentenary Jubilee Commission: The commission maintains a computer list of upcoming Columbus-related events on a state-by-state basis. Information about an individual state's events is available at no charge by contacting the commission at 1801 F St. NW, Washington D.C. 20006, 202-632-1992.

Spain '92 Foundation: For the latest information on the itinerary of the Columbus caravels, contact the foundation at 1821 Jefferson Place NW, Washington, D.C. 20036, 202-775-1992.