When it comes to having the most number of tourist arrivals, U.K.'s London and Thailand's Bangkok have always been at the top spots. The two have been going head-to-head for the last five years, and this year is projected to be no different.

For 2015, the city of London bested the competition, while Asia's Bangkok comes second, according to the MasterCard Global Destinations Cities Index.

London, holding on at the top spot for the last seven years (except 2012 and 2013 when Bangkok took the lead), is predicted to welcome 18.82 million visitors by the end of the year. Bangkok, on the other hand, is expected to have 18.24 million.

MasterCard's global index has looked into the world's most popular cities among tourists, and came out with the ranking in terms of the number of international overnight visitors -- those who are not residents of the destination city and have a stay-duration of at least one night (not using the city as a mere transit point to reach another).

Bangkok is followed by Paris at the third spot, with 16.06 million; Dubai with 14.26 million and Istanbul with 12.56 million, for the fourth and fifth spot, respectively. New York ranks no. 6 with 12.27 million, while four other Asian cities complete the top 10 with Singapore (11.88 million), Kuala Lumpur (11.12 million), Seoul with (10.35 million) and Hong Kong (8.66 million).

It is interesting to note, however, that the top five visitors from Bangkok, Singapore and Kuala Lumpur were all from the Asia-Pacific region. Apparently, there is a lack of diversity in the source of tourism arrivals in these Asian cities, as compared to countries like Instabul with half of its visitors flying in from over 30 countries, CNN reported.

The fastest growing tourist cities were from Asia as well, with Sri Lanka's Colombo experiencing the highest gain at 21.1%. It is followed by China's Chengdu (20.7%) and Abu Dhabi (20.4%) at the third spot. Lima, Peru is the only non-Asian city which joined the list at number nine with 13.9%, the highest in South America.

Matthew Driver, president for MasterCard in Southeast Asia, commented that tourism will play a vital role in Asian economies, providing a source of income and employment, CNBC noted.

The global destinations cities index also shows that London is the top city when it comes to its overnight visitors' spending. London tourists will bring in $20.23 billion, while New York City can expect $17.37 billion. The rest of the cities rounding out the top 10 is as follows: Paris ($16.61 billion), Seoul ($15.24 billion), Singapore ($14.65 billion), Barcelona ($13.86 billion), Bangkok ($12.36 billion), Kuala Lumpur ($12.02 billion), Dubai ($11.68 billion) and Istanbul ($9.37 billion).