The Lore & Language classroom is rectangular and spacious, with stone walls panelled halfway up in dark oak to soften the echo. Rows of sturdy wooden desks face a wide lectern at the front, where a large blackboard and a pair of rolling maps dominate the wall. Brass fittings on the blackboard allow it to slide upward, revealing a second slate beneath so lessons can continue without erasing what came before. Above the wooden wainscoting, tall bookcases are built directly into the stone, packed with atlases, histories, and thick dictionaries whose spines show centuries of use. The floor is warmed by a pair of long, threadbare rugs that run between the rows of desks.

The Transfiguration classroom is built to withstand the unpredictability of the art of transfiguration. Its walls are bare of decoration, save for a few high windows that allow in steady light, fractured across the room by small cracks in the glass. At the front of the room, a broad teaching platform holds a blackboard, flanked by built-in shelves stacked with an assortment of objects: candles, goblets, quills, teapots, all waiting to be reshaped in lessons. Metal cabinets at the back house larger and more unusual materials for advanced work, their doors charmed to lock themselves after hours. The floor is polished stone, swept clean but still showing hairline cracks from spells gone awry.

The entrance to House Mercator is a panelled wooden door, found in a shallow arched alcove along the second-floor corridor. The floor of the alcove is set with a stone mosaic of the house's sigil, a magpie. Two suits of armour flank the alcove, and are often heard chatting (or possibly flirting) late into the night in the common room, a common frustration for those trying to study.
On their first day, new Mercator students are brought here and taught a simple spell devised by Mercator himself: “Aperiam.” With this incantation, a student enchants an object of their choosing to act as their personal key. The magic is precise: only one object may hold the enchantment at a time. Should a student attempt to charm a second item, the first falls inert at once.
To enter, a student needs only to carry the charmed object into the alcove. The door's ward slides free with a faint click and swings open without the need for touch.

Decorated in a colour scheme of cream and light woods, an intricate network of cleaning charms is renewed annually in order to keep the Hospital Wing from taking on the physical toll that the myriad of injuries and maladies of the Penwick student body begets. A row of hospital beds lines each wall, their linens crisp and almost obnoxiously wrinkle-free. Each bed is fitted with a privacy curtain enchanted to reflect the house colours of whatever student currently occupies it. Despite what you may have heard, the curtains are not soundproofed: mind what you say behind their flimsy walls. The Hospital Wing is staffed at all hours, with young Healers-in-training occasionally performing their residencies at Penwick and covering the night shift. With the Head Nurse's permission, friends of afflicted students may be allowed to spend the night in the Wing on one of the half dozen or so indescribably uncomfortable guest chairs.