Ultra Korea officially kicked off earlier today (Korea time), but not without its share of difficulties.
Though attendees were incredibly excited to see NGHTMRE, Virtual Self, and Porter Robinson, the beginning of the day started off a bit rocky. Reports suggest that while doors were scheduled to open at 1pm, they were delayed until 3pm, disrupting sets from local openers on the main stage.
The reason for the delay appears to be that the main stage still required additional construction (pictured below). 
The Ultra Korea mainstage being set up as of 2:40pm, Korea time, June 7, 2019
Doors did eventually open and the festival thereafter reportedly went on as planned, with sets from all artists being enjoyed by tens of thousands.
The same issues are not expected to be a factor tomorrow when Josh Pan, Zeds Dead, Knife Party, and Skrillex take the main stage. (Also, what a lineup.)
via Bandwagon Asia
