As House of Holy is an ability Stand, it doesn't have any appearance to speak of. Its power manifests themselves as a a convoluted maze based on the layout and design of the building Dija Maker currently resides in.
Similar to Tenore Sax, House of Holy allows the user to manipulate any building he resides in. In the only use of this ability, a hotel is turned into a giant convoluted maze. The building is visible even to those without Stands and anyone who enters it will mysteriously disappear from this world after one hour.
When House of Holy is active, any physical damage to the building it is manipulating is ineffective.