Europe's musical capitals during the Mozart 1991 bicentennial celebration will be visited June 25 to July 10 on a trip sponsored by the Long Beach (Calif.) Mozart Festival and the Unitarian Universalist Church. Stops will be in Salzburg, Vienna, Budapest, Prague and Munich.

An itinerary includes guided walks, Mozart's birthplace in Salzburg, concerts, the Abbey of Melk, Palace Belvedere, Vienna opera house, Emperor's Palace in Vienna, Esztergom and Szentendre in Hungary and Hradcany Castle in Czechoslovakia. Cost is $1,888 per person, double occupancy, excluding air fare.Accommodations, most meals and sightseeing are part of the package. For more information, contact Atlas Travel Service, 3821 Long Beach Blvd., Long Beach, Calif. 90807.

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Seven Caribbean islands will be visited on sailings sponsored by Paquet French Cruises in March and April. Ports of call for the seven-day cruises are Iles des Saintes, Guadeloupe; Fort-de-France, Martinique; St. John's, Antigua; Bridgetown, Barbados; Castries, St. Lucia; Kingstown, St. Vincent, and Bequia, Grenadines.

Departures will take place from Martinique on March 23, and from Guadeloupe on April 6, 13, 20 and 27. Cost is from $1,690 per person, double occupancy, including air fare from Los Angeles, with ground transfers and baggage handling part of the price. For more information, contact Paquet French Cruises, 1510 S.E. 17th St., Fort Lauderdale, Fla. 33316, (800) 999-0555.

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April is the last month that a six-day trek of the Milford Track in New Zealand will be offered by Baird Reynolds of Sherman Oaks, Calif. The walks depart five times a week from Te Anau, are 33 miles long and are spread over three days. Lunches and snacks are provided by guides along the way. The trek follows the Clinton River to its source in Lake Mintaro, crosses MacKinnon Pass and descends into Arthur Valley, skirting Lake Ada and ending at Sandfly Point at the head of Milford Sound.

Cost is from $740 per person, with air fare extra. Accommodations and dinners are part of the price. The walk can be combined with other New Zealand tours that include farm- and home-stays, city packages, the Maori country, glaciers and fiords. For more information, contact Baird Reynolds, 13544 Ventura Blvd., Sherman Oaks, Calif. 91423, (800) 228-8727.

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Dominica, the largest of the Windward Islands in the Caribbean, will be the destination of a trip Feb. 23 to March 2 being sponsored by the World Wildlife Fund. Walks, swimming, bird watching, snorkeling and sightseeing to towns, national parks, waterfalls and rain forests have been planned.

An itinerary includes Portsmouth, Salybia, Castle Bruce, Emerald Pool, Trafalgar Falls, Roseau and Sulphur Springs. Air and land package from Antigua costs $1,720, with land transportation on Dominica, accommodations, meals, field trips, lectures, guides, baggage handling, service charges and basic gratuities part of the price. Membership, which costs $15 annually, is required. For more information, contact World Wildlife Fund Travel, 1250 24th St. NW, Washington, D.C. 20037.

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The national parks of Costa Rica - Monteverde, Volcan Poas, Tortuguero and Corcovado - will be the destinations of 15-day trips being offered March 2, July 20 and Dec. 21. This nature-study program will visit rain forests, active volcanoes, turtle-nesting beaches and cloud forests. Activities vary from nature walks to small-boat travel through tropical lagoons, with accommodations set for wildlife lodges and hotels.

The expedition grade is considered "comfortable" by Nature Expeditions, which also utilizes ship cabins and deluxe tent camps. Cost is $2,190, excluding air fare. Transportation in Costa Rica, transfers, most meals, sightseeing, tips for baggage handling and local guides are part of the price. For more information, contact Nature Expeditions International, 474 Willamette, P.O. Box 11496, Eugene, Ore. 97440.

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The Kuusamo Tropical Spa in Finnish Lapland will be the focus of a trip being offered March 14-23. Themed "The Enchanting World of Finnish Spas," the tour offers, in addition to six nights at the Finnish spa, two nights in Leningrad and a free stay at The Oaks or The Palms in California for five nights and six days.

Fitness classes at Kuusamo Tropical Spa will be led by Sheila Cluff, owner of The Oaks and The Palms. In Leningrad, accommodations, all meals and sightseeing at the Imperial Winter Palace and the Hermitage is provided, along with reserved seats at the ballet, opera or theater. For more information, contact Custom Spas Worldwide, 1308 Beacon St., Brookline, Mass. 02146, (800) 443-7727.

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"Masterpieces of Italy" is the theme of a 12-day trip being offered by Royal Viking Tours, 750 Battery St., San Francisco, Calif. 94111. Cities on the tour are Rome, Siena, Florence, Padua, Venice, Verona, Milan and Bellagio.

Sightseeing includes St. Peter's Basilica, the Sistine Chapel, Vatican Museum, Roman Forum, Colosseum, Medici Chapels, Cathedral of Santa Maria del Fiore, Padua Basilica de San Antonio, Michelangelo's "David," Piazza San Marco and Doge's Palace. Participants will also take a gondola cruise along the Grand Canal and a motorboat cruise on Lake Como.

Accommodations are at the Regina Baglioni-Ambassadori, Grand Hotel Villa Cora, Hotel Europa & Regina and Grand Hotel Villa Serbelloni. Cost is $4,650, excluding air fare, with departures May 18, June 1 and 15, Sept. 21 and Oct. 5. For more information, call Royal Viking Tours at (800) 426-5478.

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A tour of Europe geared to antique toy collectors is being offered by Northstar Tours of Lakeville, Minn. Focus of the trip, set for May 14-29, will be on Germany, with a minor emphasis on Switzerland and Austria. Visits will be mostly to museums in such cities as Frankfurt, Walldorf, Sinsheim, Goppingen, Zurich, Munich, Salzburg, Nurnberg, Rothenburg, Cologne, Aachen, Kommern, Dusseldorf, Trier and Wiesbaden.

An itinerary includes toy shopping and visits to toy dealers and flea markets. Cost is $2,995 per person, double occupancy, including air fare from Los Angeles, with accommodations, land transportation in Europe, museum entrance fees and breakfasts and dinners part of the price. For more information, contact Northstar Tours, Box 810, Lakeville, Minn. 55044-0810.

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Primitive tribal villages in Indonesia will be the focus of a 19-day cruise being offered by Pearl Cruises, 1510 S.E. 17th St., Fort Lauderdale, Fla. 33316. Ports of call will be on the islands of Sumatra, Java, Bali and Nias, as well as the cities of Phuket in Thailand and Penang in Malaysia. Departure from Singapore will take place April 21, July 1 and Oct. 23. Rates are from $3,150 per person, double occupancy. The July 1 trip includes round-trip air from Los Angeles. For more information, call Pearl Cruises at (800) 426-3588.