Sin City, or a Romanian castle? Where to go in 2015

Temple of Ta Prohm
Stewart Atkins | VisualSA | Getty Images

You've got vacation time accumulated, but where to go? Although hard to believe, a recent study found that many Americans don't use many—or any—of the paid vacation days they're offered.

The new year offers opportunities to venture out to one of the dozens of spots experts say are hot right now. Industry experts have plenty of suggestions about where you should go, both internationally and domestically.

Whatever your choice of destination, one thing is certain: You won't be out there alone.

Read More2015 travel hot spots: Cuba and...Russia?

The U.S. Travel Association is forecasting that there will be 2.1 billion domestic trips in 2015, with more than 78 percent being leisure travel. The organization also expects 75.1 million international travelers will be coming to the United States this year, about a 4 percent increase over 2014.

International outbound business travel from the U.S. in 2015 should increase by 6 percent, "despite the overall weaker economic outlook overseas," said Mike McCormick, executive director of the Global Business Travel Association. He said overall U.S. business travel spending will increase to 6.2 percent to $310.2 billion.

And, thanks to factors such as falling unemployment and a strengthening dollar, the ITB World Travel Trends Report 2014-2015 forecasts a 3 percent increase in overall North American outbound travel in 2015.

Many of those restless souls are expected to be millennials. Hotwire found that approximately one-third of that age group intends to travel more this year—and are budgeting a total of $226 billion for their domestic and international adventures.

"This mentality is exciting to see and we anticipate that their travel intentions will have significant impact on the industry in the coming months," Henrik Kjellberg, president of the Hotwire group, told CNBC via email.

Separately, the over-50 group may spend at least $120 billion on leisure travel, according to data from the AARP, and plans to take at least four trips in 2015

Sin City, the Catskills and...Romania?

As far as where people are planning to go, a number are placing their bets on Las Vegas.

Sin City welcomed a record of more than 40 million visitors last year, according to tourism officials. New hotels, restaurants, shows, festivals, attractions and a bevy of major conventions and trade shows may help the gambling and entertainment mecca set a new record in 2015.

Outside the U.S., American Express Travel surveyed more than 200 of its travel counselors and found that London and Santiago, Chile, are at the top of the list of popular destinations customers have already booked for 2015. Next were Paris, Mumbai and Buenos Aires.


SLS Las Vegas
Source: SLS Las Vegas

American Express' data also reported an increase in cruise bookings, with river cruising (56 percent) being in high demand.

Fodor's Go List for 2015 has recommendations ranging from New York's Hudson Valley and the Catskills (with a stop in Poughkeepsie for a stroll along the world's longest pedestrian bridge). Also included in the list were Romania (for affordable castle hopping), Singapore (celebrating its Golden Jubilee this year) and Oslo, Norway—a great place to catch a glimpse of the northern lights and the landscape that inspired Disney's "Frozen."

A survey of members of the United States Tour Operators Association named Myanmar the top destination expected to gain popularity with travelers for the third year in a row. Cuba was also on the list, along with such emerging economies as Panama, Peru, Vietnam and Cambodia.

Cuba's position right behind Myanmar underscores growing demand for travel to that country, "especially given recent news about the U.S. and Cuba reopening diplomatic relations that could include discussion of travel restrictions," association chief Terry Dale said in a statement.

Read More What's good for the dollar is good for US tourists

"Traveling to emerging destinations is definitely a trend for 2015," said travel guide Afar co-founder Joe Diaz. He advises travelers to "check out places like Battambang, Cambodia, which may soon earn [United Nations] World Heritage status, and some of lesser known islands of Indonesia."

For travel value in 2015, follow the red hot U.S. dollar.

"The US dollar has climbed dramatically against the euro and the yen, making most of Europe, Japan—and even the tiny but expensive St. Barths—more affordable than ever," Diaz said.

—Harriet Baskas is the author of seven books, including "Hidden Treasures: What Museums Can't or Won't Show You," and the Stuck at the Airport blog. Follow her on Twitter at @hbaskas . Follow Road Warrior at @CNBCtravel.