15 stunning photos of the world's most interesting cities

Alejandro Merizalde/National Geographic Travel Photographer of the Year Contest

Paris, Ile-de-France, France

This year's National Geographic Travel Photographer of the Year contest is now officially accepting entries, and the submissions that have already come in are pretty mind-blowing.

There are three categories to which photographers can submit their work: nature, cities, and people.

The grand prize winner will be named the 2016 National Geographic Travel Photographer of the Year and get a seven-day Polar Bear Safari for two at Churchill Wild - Seal River Heritage Lodge in Manitoba, Canada. Airfare is included.

Below, see 15 submissions to the "Cities" category. The contest ends May 27.