The small upper windows cast but a chill and feeble light into the vast cavern, so that the choir and chapels are buried in perpetual twilight. The windows in the vestibule do very little towards the illumination of the interior. At the extremity of the nave, which is raised on steps to form a choir, anciently stood the high altar, but this has been removed. Above, where it was can be discerned faintly through the obscurity, a bas-relief rudely sculptured, but very curious. It occupies the entire width of the choir; on the right is an angel playing upon a stringed instrument, with outspread wings, as if in the attitude of soaring, and on the left, perched on a rock, is a monstrous animal with gaping jaws, bristling mane, and raised paws. In the midst of the group is a little old man armed with a stick, apparently repelling this monster. It has been conjectured that this is intended as a representation of the saint himself ready to deliver his votaries from the jaws of Hell. But it is more probable that the whole subject is allegorical of Death, armed with his scythe between the powers of Light and of Darkness. The choir arch is one of the boldest and most original conceptions in this marvellous temple. It consists of two gigantic angels carved out of the sandstone, with their feet upon the piers on each side, and their heads nearly meeting at the crown of the vault. Each has four wings, the two smaller wings are raised about their heads, forming a nimbus to each. The other two wings are depressed. These mighty angels were formerly whitened and partially gilt, and the effect of the great figures looming out of the dark vault is most impressive. On the right side of the nave, at the spring of the arches, between two of the piers, is a centaur armed with a bow, cut in the stone, and on the opposite spandril are two goats, disposed back to back, also cut in the rock. On one of the piers is an inscription graven regarding the dedication of the church, but unfortunately the date is illegible. The exterior of the church is adorned with a noble portal, richly sculptured, of much later date than the church within. On entering the church through this rich portal a feeling of astonishment comes over one. The exterior in no way corresponds with the interior, which is void of ornament. The piers are massive parallelograms without mouldings, the arches between them semicircular, stilted, perfectly plain; a string alone marks the rise of the arch from the pier. In the floor of one of the aisles is a hole through which a descent was anciently made into the crypt below the church; this crypt also is hewn in the solid rock, and has a funnel-shaped dome, a spiral flight of steps was cut in the rock round it descending from the church into the crypt. The descent must have been hazardous in the extreme unless the stairs were provided with a balustrade, of which at present no trace remains.