Ghent is one of those Belgian cities that often gets overlooked, with only shy of 250k people living there, it is most definitely a hidden gem.
Not only does it have untouched architecture, it also boasts a wide varity of churches and a castle (yes, a real castle!)
I myself lived in Ghent for about 2 years and have been through Ghent at least twice a week for half my life. It is one of my favorite places on earth.