The steps leading up to the Altar are paved with Purbeck, Sicilian, and black Derbyshire marbles. The spaces between the steps are decorated with a series of scriptural subjects in inlaid work in black and white marble, with distinctive inscriptions. The Altar is of oak, with a single slab of Belgian marble for its top. On the sides of the Altar are deeply carved panels; that in the centre represents the Lamb with the Banner, the other panels contain the emblems of the four Evangelists.
The organ stands in a special chamber on the north side; the carved front was not put in place till 1890. It was designed by Mr. J. Oldrid Scott, a son of Sir Gilbert Scott. In 1635 the famous Robert Dallam of Westminster built a "paire of new orgaines" for the College. The organ has been repeatedly enlarged, altered, and improved; it may be that some of Dallam's work still remains, though this is uncertain. The present organ is one of the best in Cambridge; its tone throughout is uniformly beautiful.
The brass reading-desk was given to the old Chapel by the Rev. Thomas Whytehead, a Fellow of the College; the pedestal is copied from the wooden lectern in Ramsay Church, Huntingdonshire; the finials, which are there wanting, having been restored, and the wooden desk replaced by an eagle.
As we return to the Ante-Chapel we may note the great west window, representing the Last Judgment; this was given by the Bachelors and Undergraduates of the College. There are also windows in the Ante-Chapel to the memory of Dr. Ralph Tatham, Master of the College, and to the Rev. J. J. Blunt, Lady Margaret Professor of Divinity.
The oil-painting which hangs on the south wall of the Ante-Chapel near the door--a Descent from the Cross--is by Anthony Raphael Mengs. It was given to the College in 1841 by the Right Hon. Robert Henry Clive, M.P. for Shropshire.
We enter the Hall from the Screens, between the First and Second Courts. The southern end is part of the original building of the College. It was at first about seventy feet long, with one oriel only, the old Combination Room being beyond it. When the new Chapel was built the Hall was lengthened, and the second oriel window added. The oak panelling is of the old "linen" pattern, and dates from the sixteenth century; that lining the north wall, beyond the High Table, is very elaborately carved, being the finest example of such work in Cambridge. Within living memory all this oak work was painted green. The fine timbered roof has a lantern turret, beneath which, until 1865, stood an open charcoal brazier. From allusions in early documents it would appear that members of the Society gathered round the brazier for conversation after meals. In addition to its use as a dining-room, the Hall also served as a lecture-room, and for the production of stage plays. On these latter occasions it seems to have been specially decorated, for Roger Ascham, writing 1st October 1550, from Antwerp, to his brother Fellow, Edward Raven, tried to picture to him the magnificence of the city by saying that it surpassed all others which he had visited, as much as the Hall at St. John's, when decorated for a play at Christmas, surpassed its appearance at ordinary times.