Most popular cities to visit in 2015

Crowds of tourist gather outside Buckingham Palace, London.
David Williams | Gallo Images | Getty Images

If you're looking to beat the crowds over the summer holidays, you may want to leave these cities off your travel itinerary.

London is predicted to be the most frequented destination by travelers this year, according to the MasterCard Global Destinations Cities Index published on Wednesday, with 18.82 million visitors expected to spend time in the city in 2015.

The U.K. capital has topped the Index in five out of seven years, except 2012 and 2013, when Bangkok held the lead position. This year, Bangkok is forecast to welcome 18.24 million travelers, putting it in second place.

The MasterCard Global Destinations Cities Index provides a ranking of the 132 most visited cities from around the world in terms of international overnight visitor arrivals.

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Paris, Dubai and Istanbul claimed the third, fourth and fifth spots, with 16.06 million, 14.26 million and 12.56 million visitors, respectively, expected this year.

Meanwhile, New York, Singapore, Kuala Lumpur, Seoul, and Hong Kong rounded out the top ten.

The up-and-coming tourist spots

While the top ten represent well-established tourist cities, the fastest-growing destinations present a more exotic picture.

Seven of the top ten fastest-growing cities by visitor numbers are in Asia.

Sri Lanka's capital city, Colombo, leads the pack, logging a compound annual growth rate (CAGR) of 21.1 percent over the last six years, followed by Chengdu, the provincial capital of China's Sichuan province, with a CAGR of 20.7 percent

"Tourism is becoming an increasingly important source of income and employment for many Asian countries. This reflects the growing appeal of Asia as it continues to develop, led by the fast emerging ASEAN economies, China and India," Matthew Driver, president, Southeast Asia for MasterCard, commented.

"As countries compete for tourist receipts, and seek to improve the visitor experience, it will be key for governments and tourist authorities to continue to invest in smarter city infrastructure while preserving and protecting the heritage - from monuments to cultural events - that makes their cities unique," Driver said.

Osaka has seen the third fastest growth in visitor numbers thanks to an influx in tourists from China, followed by Xi An and Taipei in fourth and fifth place, respectively.