Janssens Cathedral Victorian Greenhouse with Large CupolaJanssens Cathedral Victorian Greenhouse with Large Cupola The Cathedral is one of our largest greenhouses, distinguished from other Janssens models by a cupola that adds both height and curb appeal. It features a wider footprint than the Royal Victorian line, making for a significantly more floorspace than even the VI 46. Like all Janssens models its 4mm tempered glass and aluminum frame make it resilient enough to withstand wind gusts and most hail.