Mysterious Circle In The Sky

In one afternoon in February 2014, a mysterious sight appeared in the sky. A circle formed around some clouds above  Mactan Island, in Cebu, Philippines.

While riding a ferryboat 
from the port of Cebu city 
to the nearby Mactan island, 
the sky above looked as usual as any day. 
But when the ferry was about to dock 
after about 20 minutes less, 
this mysterious formation 
caught my attention. 
It was a huge circle i never seen before. 
I had no idea why it was there, 
or how it was formed, 
but i was amazed at the sight. 
Up to this day, 
i don't know what it was. 
Here's the video of the mysterious circle 
i posted on Youtube.