A villa in the Holy Capital. It was made around the same time as the royal palace so it houses a similar appearance.
Each door has a door viewer, similar to doors meant for house entrances.
The family heirloom is utilized along with the layout of this villa to create a labyrinth:
"The legendary labyrinth back in [the March Turmoil] consists of two layers—the inner layer consisting of the villa and the outer layer encompassing the streets and byways outside. The effect of the artifact veils the two layers in fog and partitions them into numerous sections. Whenever a person passes through the boundary of a section, he would be randomly teleported into another section. Unless the person enters the labyrinth in a specific manner at a specific timing, they will never be able to reach their destination. That’s also why it was termed as a labyrinth.
As for the inner layer, it works in the same manner as the outer layer, just that the boundaries are the doors this time around, making every single one of them an ‘entrance’. I heard that huge, bulky metal doors were used back in that era, but they have already been replaced with the ordinary wooden doors you currently see. Nevertheless, we still kept the door viewers around for remembrance’s sake."
Currently, it is impossible to recreate the same labyrinth as of the March Turmoil era but Roel mentioned that it is possible if limited to the interiors.