Castell Coch, so called from the red tint of its materials, is, in general plan, a triangle, each angle being capped by a drum tower. Its general divisions are the south, east, and northern towers, the gate tower, the curtains and hall, and the outworks.
The platform occupied by the whole is about 200 yards long by 70 yards broad, and the principal works of the castle occupy its west end. The south face is, in part, precipitous, and from 20 feet to 30 feet high. The north face, towards the upper hill-side, is deepened into a formidable moat, and the east end was defended by a fosse, cut deeply across the rock, and beyond this by two towers, connected by a curtain wall.
The North Tower rises from a square base to a cylindrical superstructure, the north and south angles terminating in buttresses, each the half of a pyramid cut vertically and diagonally across, after a fashion very common in Welsh castles, and well seen in Marten’s tower at Chepstow. The cylinder is 40 feet in diameter. It contains three stories, of which the middle one is on a level with the inner court, or terre-plein, of the place.
The lower story may have been a cellar. It is vaulted, and has two great cross-springer ribs, and two windows opening high above the floor. A narrow passage, vaulted, with steps, leads into it from the court. Its internal diameter is 18 feet, its walls upwards of 10 feet thick. The windows were mere loopholes.
The middle story is also circular and vaulted, with similar ribs. Here, however, the windows open nearly on the level of the floor, though also loops. There is a fireplace, with a flue carried up in the wall. The flue is backed with stone. The entrance to this chamber is also from the court, and, on the east side of the vaulted passage, a gallery passes off in the thickness of the wall, and leads to what was a small garderobe, occupying a square projection on the east side of the tower, at its junction with the curtain. The general dimensions of this story, and the thickness of the walls, correspond with those of the room below.
The upper story contains one chamber, the south and east sides of which are flat, the rest circular. Here are no less than three fireplaces, each of large dimensions, with funnels in the thickness of the wall. It contains also two small recesses, one a sort of sink, and has two windows. There are also two doors, one, on the south side, opening upon the roof and ramparts of the hall and west front, the other, eastwards, leading to the ramparts of the great or northern curtain. Access to this chamber, from below, seems to have been obtained by an exterior stair between the tower and the hall. This story, within, is about 26 feet mean diameter, and the walls vary from 2 feet 3 inches to 4 feet thick. It was roofed flat, with timber, and above were ramparts and a parapet, probably reached by means of a trap-door in the roof. It was evidently the kitchen, here, as at Morlais and Coningsburgh, placed in an upper floor.
This tower is the most perfect of the whole, and in tolerable preservation, although the lower chamber is half full of rubbish; the small apartment connected with the middle story is broken down, and the roof and ramparts are wanting on the summit. This tower, however, is evidently the type of, and has served in the present instance as a clue to, the original plan of the others.
The South Tower corresponded nearly to the last, and, like it, appears to have contained three chambers, and at its junction with the west curtain, a square projection, containing in the middle story a small garderobe, and in the upper, probably a communication with the battlements of the hall. The lower chamber is entered by a vaulted passage, down steps, from the courtyard. The middle or main chamber probably was entered on the level, by a passage from the courtyard, and a mural gallery seems to have led from this passage to the window or opening in the south end of the hall. The upper chamber was accessible from the hall battlements, as it probably also was from those of the gateway curtain. It is uncertain whether this tower rose from a square base—probably it did. Its upper part was cylindrical, 40 feet diameter. The walls are 8 feet thick, and the chambers do not appear to have been vaulted. This tower is in a ruined state. The two outer thirds of its circumference have been blown away by a mine, but the part connected with the hall, including a door below, two windows in the lower and middle story, and the small chamber in the wall, remain tolerably perfect, and remove all doubts as to the original elevation and particulars of the whole.
The East Tower corresponds in altitude and general arrangements to the other two, like them containing three stories. It is cylindrical from the base, and 40 feet diameter; but, towards the courtyard, it presents a flat face, with two shoulders projecting at its junction with its curtains. Like the other towers, it has a square projection for a small chamber, here found at its junction outside with the great or northern curtain. The lower story, like those of the other towers, is below the level of the court, but instead of being entered directly by a distinct staircase, a gallery branches off from the passage to the middle chamber, and descends, winding in the thickness of the wall, to a vaulted prison below. This lower chamber is filled up, but its existence is evident enough, and the staircase is seen through a great rent in the wall. The diameter is 18 feet 4 inches, and the thickness of the wall 10 feet 10 inches.
The first floor is entered by a passage from the court, on a level. This chamber had two loops. There is no fireplace, and no trace of a vault, although the walls are above 10 feet thick. On either hand, opening out of the passage leading to this chamber, are galleries in the wall, that on the right descending to the chamber below, that on the left running on a level, to open into a small chamber in the square projection between the tower and the great curtain. Here seems to have been the well. The upper chamber appears to have been entered from the ramparts by a long pointed doorway in the gorge; and over the lower door, leading from this, on the right, a passage leads to a spiral stair in the wall, which evidently gave access to the battlements of the tower. This tower has been rent asunder by a central explosion, but the outer part has only shifted a little.