Use Gyeongbuk subway station and walk to the front of the palace to observe this view. Gwanghwamoon is located close by.
Take extra care and use common sense during electrical storms such as these.
I managed to capture this wild electrical storm luckily with bracketing. The lightning flashes only lasted about a minute in total, and I managed to take 3 sets of 5 bracketed exposures. This one turned out the best out of the 15 taken. Noise reduction, and curve adjustments were done in Photoshop CS5.