its length, at , which makes it impossible to be viewed in its entirety, disguises variations in the plan caused by the Pennants' desire to incorporate, rather than demolish, elements both of the original medieval house, and Wyatt's earlier castle. The main building material is local rubble, lined internally with brick and externally with limestone ashlar. The masonry is of exceptional quality. The main entrance to the castle is by way of a long drive which transverses the length of the castle before doubling back and passing through a gatehouse into a cour d'honneur in front of the central block. Interior Grand Hall The house is entered through a low entrance gallery. This leads into the Grand Hall, which Pevsner considers "a strikingly inventive piece of architecture". Of double height, it resembles the nave or transept of a church. The ceiling forms a triforium supported by compound columns. The hall acts as a junction, to the left entry is to the keep and the family apartments, to the right, the service wing, and ahead stand the state apartments of the main block. A 20th century critic described it as, "about as homely as a railway terminus, admirably suited to house an exhibition of locomotives, or outsize dinosaurs." The stained glass is by Thomas Willement. Library Mark Purcell, in his 2019 study, The Country House Library, describes the library at Penrhyn as "not just gargantuan, but exotically and astonishingly opulent." The room is very large and bisected by four, flattened arches. These are plaster, as is the ceiling, but grained and polished to appear as wood. Their decoration, and the design of the arches, draws on that found at the genuinely Norman Church of St Peter at Tickencote in Rutland. The room contains a billiard table constructed entirely of slate and a range of bookcases and furniture designed by Hopper. Haslam, Orbach and Voelcker consider the library the precursor for a long subsequent history of "masculine rooms [for] millionaires". The room still contains the basis of a "good gentleman's library", despite sales of some of the most important and valuable books in the 1950s. Drawing Room and Ebony Room The Drawing Room is the reconstructed Great hall of the medieval house, which Samuel Wyatt had previously incorporated into his late 18th-century remodelling. It follows the library in its vaulting and panelling but the decorative style is lighter and more feminine, reflecting