Babak Castle, Kalibar.
People of all fitness level can get up to the top. Even though the castle appears to be sitting up on a ridiculously high mountain top, it’s actually an easy climb. If anything, it’s a nice, steep-ish walk and once you get close to the mountain there’s stairs you can use to get to the top.
Once up top you’ll be greeted by stunning lush green mountains (I was there in the month of May) in all directions. The walls of the castle are thick which means you can safely stand on those to take photos. However, for those who have fear of heights, be carefully and don’t fall. I felt dizzy just looking down so I decided to just get off those walls haha.