I found the Starfield Library in the Starfield COEX Mall to be pretty amazing and cool, unlike anything in Australia, and it's highly recommended as one of the most Instagrammed places in Seoul.
I found Gwangjang Market to be amazing for food, with the tteokbokki and japchae being the best I've ever had, and the handmade noodles were highly recommended for their juiciness and broth.
I highly recommend KyoChon Pelbang, a hidden chicken speakeasy, because the chicken was to die for, the tteokbokki was amazing despite being very spicy, and the makgeolli was also on point.
I found the fluffy pancakes at 5 to 7 to be the best I've ever had, melting in my mouth and surpassing even Japanese versions, making it a definite must-visit in Seoul.