I remember doing a temple stay just outside of gyeongju at bulguksa several years ago. It was an awesome yet terrible experience all at the same time. It was a 3 day/2 night stay, we had to be in bed by 9 pm each night and awoke at 4 am to climb the mountain to see the first sunlight and do the 108 bow worship.
On top of that we had to wash out or food bowls and clean them with a piece of kimchi and consume the excess as to teach giving thanks for nourishment. It was difficult and and challenging but something I will always remember. I have a new found praise for the monks that live this life.
Besides the occasional train through gyeongju or going to the waterpark there, I havent done much else, need to visit more often