The photo, ‘Colorful work,’ was taken in November last year and shows a worker preparing an 18-meter-long hot air balloon during a tourism festival in Ba Vi National Park on the outskirts of Hanoi.

Viet said it took the worker more than an hour to complete the preparations. "I spent many days attending the festival and got up around 5 a.m. and traveled more than 100 km each day, waiting for this moment."

In recent years hot-air ballooning has become increasingly popular at festivals in Hue, Hoi An, Da Nang, Hanoi, and Ho Chi Minh City, Vietnam's major tourist attractions.

The annual photo contest is organized by Smithsonian magazine, the official journal published by the U.S.’s Smithsonian Institution, the world's largest museum, education and research institution. This year it received 45,000 submissions from 145 countries and territories.

Tran Tuan Viet, 38, is an avid photographer who travels around the country taking pictures of landscapes and cultural features. Many of his shots have been featured in the U.S.’s NatGeo magazine.

In 2018 Vietnamese lensman Nguyen Huu Thong won the grand prize in the Smithsonian photo contest for his ‘Flea Market Breakfast’ taken in a rural market in Ha Giang Province.