NEW ORLEANS — The city never shakes off its playful mood. Calliope music toots from the steamboat Natchez. Dixieland jazz pours all over Bourbon Street. Streetcars clang along Canal and St. Charles. Carriage drivers call off the historic sights, while their mules clip-clop along. Mimes constitute the only silent element, but even they tend to wear loud outfits.

Tons of purple, gold and green stuff overflow the merchants' counters. Purple, gold and green are the colors of Mardi Gras. They're on beads, masks, costumes, plastic go-cups and anything else that may or may not be Carnival-related.

New Orleans is always on purple, gold and green alert, so outsiders can't possibly forget they're in the one place that puts on the biggest and most hell-raising Mardi Gras in the U.S.

City gone slightly mad

Mardi Gras, either in person or as seen on TV, looks like an entire metropolis gone slightly mad — huge crowds lining the streets to see massive floats bearing grotesque figureheads, and floatloads of costumed party animals tossing beads at outstretched arms. Mardi Gras means louder bands, more lithe baton twirlers and outrageous behavior than halftime at the Superdome.

Mardi Gras season Where Although Carnival season began Jan. 6 (Twelfth Night), parading starts today and continues on through Feb. 8. The largest and most lavish parades take to the streets Feb. 4 through Feb. 8. Temperatures can range from the tolerable 50s to the pleasant 70s, with warmer weather generally the norm. Lodging Beverly Gianna of the city Convention and Visitors Bureau (see numbers below) says there's still time to find hotel accommodations for any part of Carnival season. "More and more people are making last-minute decisions about everything," she notes, "and we have added a lot more rooms." More information Arthur Hardy, an expert on all things Mardi Gras, maintains an informative Web site, www.mardigrasguide.com, and publishes an annual $7 magazine-style guide that can be ordered online. Blaine Kern's Mardi Gras World is at 233 Newton St., New Orleans, LA 70114-5727; 800-362-8213; fax 504-368-4628; www.mardigrasworld.com. Tours cost $15 for adults, $11 for seniors and students with school ID. For children 11 and under, it's $7.25. Reservations required for groups of 10 or more. For more information and suggestions for accommodations and dining, contact the New Orleans Metropolitan Convention and Visitors Bureau, 877-791-8272; www.neworleanscvb.com.

"The crowds number 1-1/2 to 2 million people over parade routes that might be 6 miles long," said Capt. Marlon Defillo, who oversees Mardi Gras for the city's police department. "In some cases, they're standing at the curbs four deep. When we're 13 days out, we go to 12-hour shifts. All vacations are canceled. We deploy 1,800 officers, including reserves, half for Mardi Gras and half for the rest of the city. For the last five days, we bring in other agencies."

Festivities start around Jan. 6 every year, Twelfth Night, and this year will ramble on through Mardi Gras — Fat Tuesday — on Feb. 8. Parades happen almost every night. People attend scores of balls, parties and soirees. Parade groups — social clubs called krewes — commission elaborate floats. By late autumn of the year preceding Mardi Gras, one might expect to find the city in a frenzy of preparation.

But no. This has gone on far too long for any sort of panic. New Orleans has staged Mardi Gras since 1743, except during the Civil War, an 1875 period of civil unrest and the two World Wars.

The Krewe of Rex

Toward the end of last year, I talked with a supremely calm gentleman named King Logan, an officer of the krewe called Rex.

Krewe is a term coined in 1857 by a group called the Mistik Krewe of Comus. Members believed their mysterious ways deserved some wacky spelling. They staged the first New Orleans themed parade, complete with floats and masked men in costume. Komus, in Greek, means "to revel," and the theme was John Milton's "Paradise Lost."

The Krewe of Rex hit the streets in 1872 and managed to tame previously rowdy Mardi Gras celebrations into a relatively orderly fete. Its king, Rex, became monarch of all Mardi Gras.

When Rex takes to the streets on Mardi Gras day, the people on the floats may appear carefree as they toss beads, cups and specially minted aluminum doubloons. They might be letting their hair down because some of them have been involved in hours of preparation over several months. That $400 to $500 each float rider spends on beads and other trinkets is the least of it.

However, they also see to it — "with almost military precision" — that the police know exactly what the Rex parade will do and where it will go, that all the proper permits have been obtained, floats designed and built, costumes sewn and those trinkets, or "throws," purchased. Rex coined the first Mardi Gras doubloon in 1960, an aluminum disk stamped with a design symbolizing each year's theme.

Krewes host various functions leading up to the parade — luncheons, for example, to thank the police, fire department and the media for their support. Someone is in charge of designing the ducal insignia that adorns proclamations and ball invitations. Somebody else oversees the stable where the parade horses are kept. And so on.

Mardi Gras World

To find anything resembling a beehive of pre-Mardi Gras activity, I had to cross the Mississippi and make my way to Blaine Kern's Mardi Gras World.

The company creates and manufactures Mardi Gras-season floats and other bigger-than-life displays. A vast collection of sheds and warehouses, Mardi Gras World looks pretty much like an industrial park — if industrial parks had giant plastic alligators in the parking lots and if the forklifts hauled grinning cartoon heads the size of Volkswagens.

In olden days, krewes imported their floats and other parade materials from Paris. Eventually, sharp-eyed entrepreneurs figured they could do the job here at home. In 1947, Blaine Kern jumped on the Mardi Gras industry bandwagon and built the largest company in the field.

Kern said Mardi Gras accounts for only 30 percent of the company's revenue. Guided tours and parties bring in 40 percent. The other 30 percent comes from non-Mardi Gras floats commissioned by the likes of Red Baron Pizza and Capt. Morgan's Rum for appearances in parades around the country. Other figures go to theme parks and Las Vegas enterprises.