On April 7 visitors lined up at the Ancient Man Cave entrance to photograph the butterflies.

Staff said the park is busy even on weekdays.

Visitors in April said crowds and traffic were already building by around 10 a.m. on weekdays.

For the best experience, visitors from Hanoi should leave by 5 a.m. to reach the park by 7:30 a.m. and avoid the crowds.

Butterflies are easier to photograph before the sun gets too hot since they tend to shelter in the shade as temperatures rise.

Photo by Nhan Hung