Cruising Russia's HeartlandChances are that when you hear the word "cruise," the Upper Volga does not spring readily to mind. A week-long trip along that river is the focus of an upcoming Smithsonian study tour to the Soviet Union. You can leave from New York Aug. 18 and visit Leningrad and either Georgia or Estonia before heading for Moscow for the Aug. 29 cruise departure (cost $5,885), or you can leave New York a week later and spend three days in Moscow prior to the cruise departure ($4,395). For information: 357-4700.

Nixon on FileLet's make one thing crystal clear: The Richard Nixon Library and Birthplace opens to the public on Friday, after a private dedication ceremony on Thursday that Nixon and his family, President George Bush and former presidents Reagan and Ford are expected to attend. The nine-acre museum site -- located near Anaheim, Calif., in Yorba Linda -- will feature Nixon's birth house, a 52,000-square-foot Spanish-style library and museum and four gardens. Included in the museum are a 292-seat theater, a biographical gallery, a re-creation of the Lincoln Sitting Room and a Watergate area, where visitors can hear excerpts from the White House tapes. Admission is $3.95 for adults, $2 for seniors and free for children 11 and under. For information: 18001 Yorba Linda Blvd., Yorba Linda, Calif. 92686, (714) 993-3393.

Birding Breaks in IrelandThe winter skies of Ireland are home to a wide range of birds -- wild fowl, shore birds, woodland and river species, all of which will be the focus of two week-long tours of the east coast in November and February. Transatlantic birders are guaranteed to spot about 60 new species. Costs start at $1,185 and $1,250, not including airfare. For information: Irish Birdwatch Tours Ltd., 22 Butterfield Park, Rathfarnham, Dublin 14, Republic of Ireland, phone 011-353-1-852-469.

TRAVEL TRIVIAName the Irish counties that go with these hints: A television doctor; a type of crystal; a bottle stopper; a nonsense poem; a woman's name; a word heard in a deli. ANSWER BELOWTRIVIA ANSWER: KILDARE; WATERFORD; CORK; LIMERICK; CLARE OR KERRY; MAYO

CRUISE VIEWSCommodore Cruise Line offers four special celebrations aboard the Caribe this fall. Country music will be the focus of two week-long cruises, departing Miami Sept. 8 and 15, with headlining act Patty Loveless. Oktoberfest will be celebrated on two week-long cruises, departing Miami Oct. 13 and 20. Rates begin at $625 per person. For details: 1-800-832-1122.

FAIR WARNINGSThe Salzburg Festival, Salzburg, Austria, July 27-Aug. 31.

Dodge City Days, Dodge City, Kan., July 27-Aug. 5.

Swiss National Day, nationwide, Aug. 1.

63rd Annual Mountain Dance and Folk Festival, Aug. 2-4, Asheville, N.C.

57th Annual Craftsmen's Fair, Mt. Sunapee State Park, Newbury, N.H., Aug. 4-12.

Folklorama -- Canada's Festival of Nations, Winnipeg, Manitoba, Aug. 5-18.

Inter-Tribal Indian Ceremonial, Gallup, N.M., Aug. 7-12.

Sail Amsterdam, Aug. 9-14.

The Edinburgh International Festival, Aug. 12-Sept. 2, with performances and recitals from around the world and highlighting those from Eastern Europe and the Pacific.