Click on photos to enlarge.
Notes in italics from Oxfordshire by Jennifer Sherwood and Nikolaus Pevsner (1974)
Yale University Press, New Haven and London.

At Carfax is the tower of the church of St Martin demolished in 1896. To the E is a C19 doorway and a clock with quarter jacks. The higher stair-turret is C19 too. ...
Range of houses in the High Street. The red gabled town house is 17th century. The seeming 18th century house beyond with the canted bays is in fact 1970. The flat-fronted house beyond that is 1976. In the far right of the middle picture an imitation Tudor range of 1901. 
In Oriel Street (off the High Street) a row of stuccoed houses. The blue house is c.1714 (source), the others appear to be the same period.

In first picture the frontage of Balliol College with, next to it, the entrance to Trinity College and 17th century cottages belonging to Trinity, also seen in the second picture. In the last picture, part of the range of houses opposite Balliol. 

All Saints church at the end. The house with bay windows: Lincoln House, 1939 by Sir Hubert Worthington and G.T. Gardner, a perfectly normal three-storeyed town house with shops and bay-windows, rendered. Across the street, the new Rector's Lodgings, 1929-30 by Herbert Read, well-meant neo-Early-Georgian and no harm done.

In Cornmarket Street  the The Golden Cross Inn ... has medieval and C17 evidence of much interest. All this is in the yard, not on the front. The N range is C15 with original oriel windows. The S range is later C17 with two-storeyed oriels with Ipswich windows. Four gables of three different sizes. ... No longer an inn.
28 Cornmarket Street, on the corner of Ship Street. Timber-framed, late-medieval town house, built c.1470 and restored 1952.
St Michael's church on the opposite corner. The W tower is late Anglo-Saxon, probably of c.1000-50. Long and short quoins and two tiers of twin bell-openings with bulgy balusters and through-stones.
More at the church's website.

Ship Street has an unspoiled stretch of modest houses facing Jesus College.

The 18th century facades of Holywell Street. They hide many older buildings.

Beaumont Street was laid out in 1828 on the site of the old Beaumont Palace. It makes the finest street ensemble in Oxford. Long terraces of three-storeyed ashlar-faced houses, some with door surrounds with columns and broken pediments, many with iron balconies, a few with verandas instead, i.e. canopied balconies. ...

In St Michael's Street Vanbrugh House, almost a parody of Blenheim. Ashlar, five bays and three storeys, with a slight one-bay projection. The top windows are segment-headed, the first-floor windows have squared aprons. but the Brobdingnagian spirit of Blenheim - Vanbrugh and Swift represent the same generation - inspires the centre bay only. Two broad giant pilasters each with a bit of entablature on top - just one triglyph - carry a cornice as deep as though it were a canopy and existing only in that bay. Above it the second floor runs through as if nothing had happened. The doorway and the window above it have big triple keystones. ...
In George Street former Corn Exchange ... brick and stone, Gothic, with a tower with steep hipped top and office buildings l. and r. (H.W. Moore 1894).

In Paradise Street the one high remaining tower of the castle. This is a wall-tower really belonging to the curtain wall, and the date assigned to it by the RCHM (Royal Commission on Historical Monuments), i.e. the late C11, seems too early. The tower is of four stages, slightly receding and has a diagonally set staircase in the SE angle. ... High up on the E wall are remains of large round-headed windows. ...
More about the castle at Oxford Archaeology (where evidence suggests mid C11 for the tower, i.e. before the Norman castle)

In New Inn Hall Street, belonging to St Peter's College, the former rectory, a fine, plain Georgian house of five bays and two and a half storeys with lower one-bay appendices - all very smooth ashlar work. Porch with Tuscan columns and pediment. Arched ground floor-windows.
S of the rectory is Hannington Hall ... of 1832 by Thomas Greenshields, altered in 1897-8 by Walter K. Shirley and remodelled for the use of St. Peter's College. Front of five bays, ashlar-faced, with bays one and five flanked by giant pilasters. In the N wall high up the Venetian window of the dining hall of the college.
Former Girls' Central School, 1901 by Leonard Stokes. An impressive, though not a large building. The centre is recessed and a little sunk. It is of two storeys with a cupola with diagonally set columns. The ground floor is a continuous strip of nine cross-windows, grouped in threes. Above, only three small four-light windows. The projecting wings are higher, and their doors are set into niches of banded rustication (á la Wren). It is not really like any other Oxford building.

Jackson Wing of the Radcliffe Science Library, 1901 by Sir Thomas G. Jackson. Six bays and a slight projection with giant pilasters, a pediment, and a large upper Venetian window. The long range has buttresses and mullioned and transomed windows bound together with arches at the very top.
Rhodes House was established by the will of Cecil Rhodes as a centre for at any one time 96 scholars from the United States, 60 from the British Empire, and 15 from Germany (Rhodes Scholars ). In 1929 Sir Herbert Baker designed the present building ... Squared rubble in small blocks with ashlar dressings in more or less the same colour. It had no Oxford tradition. ... Rhodes House has a very odd 'parti' of a large Cotswold mansion of the late C17, with mullioned and transomed windows, balustrade and hipped roof, and set between its two front wings a small classical rotunda with portico. ... The building is an oddity, but it has personality enough to rouse affection in some. ...

Oxford University's Manor Road Building by Sir Norman Foster, 1999. On the opposite side of the road, Victorian or Edwardian gabled brick buildings.

Parsons' Almshouses, built in 1816 ... now part of University College. ... Two-storeyed, Tudor, six bays, with two entrances. Opposite, a rubble-built late C16 to C17 house with two timber-framed gables. Oriels in the gables. One original five-light mullioned stone window. Beyond the Almshouses the former Tutor's House, 1887 by H.W. Moore ... of brick, with shaped gables and Arts and Crafts detail - quite pretty. Finally at the end a pretty house with balcony facing down the street.