Question: What distinctive surface is the historic Merton Street, that runs parallel to High Street in the southeastern university city of Oxford, England?

Context articles: Magpie Lane, Oxford
Eastgate Hotel
Logic Lane
Merton Abbey, London
Peas Hill
Merton Street
Hope Street, Liverpool
Merton Street tennis court
Oxford
Dead Man's Walk, Oxford

Magpie Lane is a narrow historic lane in central Oxford, England.
 It leads south from the High Street where it is at its narrowest, now completely pedestrianised as a pavement, and north from the cobbled Merton Street.
The Mercure Eastgate Hotel (aka The Eastgate locally) is a hotel located in the historic university city of Oxford, England.
 It is located on the south side of Oxford's High Street near to the Ruskin School of Drawing and Fine Art and the Examination Schools of Oxford University.
Logic Lane is a small historic cobbled lane through University College in Oxford, England, so-called because it was the location of a school of logicians.
 It links the High Street at the front of the college with Merton Street to the rear, which is also cobbled.
 Logic Lane covered bridge is a short covered bridge over the lane at the High Street end (see below).
Merton Abbey is an area in southwest London, England.
 It lies between South Wimbledon and Colliers Wood in the London Borough of Merton.
 Merton Abbey takes its name from Merton Priory, which once stood on the northern edge of the district.
 The area is bounded by Merton High Street to the north, the River Wandle to the west, Christchurch Road to the east and Deen City Farm to the south.
Peas Hill is a street in central Cambridge, England.
 It runs between Wheeler Street to the south and Market Hill to the north.
 King's Parade runs parallel with the street to the west.
 Guildhall Street runs parallel to the east.
Merton Street is a historic and picturesque cobbled street in central Oxford, England.
 It joins the High Street at its northeastern end, between the Ruskin School of Drawing and Fine Art (together with the Examination Schools) and the Eastgate Hotel at the historic east gate of the city.
 It then runs east-west, parallel and to the south of the High Street for most of its length.
Hope Street, Liverpool, England stretches from the city's Roman Catholic cathedral, past the Anglican cathedral to Upper Parliament Street and it is the local high street of the Canning Georgian Quarter.
 It contains various restaurants, hotels and bars and is one of Liverpool's official 'Great Streets' and was also awarded 'The Great Street Award' in the 2012 Urbanism Awards, judging it to be the best street in the country.
 The road runs parallel to Rodney Street (the "Harley Street" of the north).
 Together with Gambier Terrace and Rodney Street it forms the Rodney Street conservation area.
Merton Street tennis court is the home of the Oxford University Real Tennis Club.
 It stands on the north side of Merton Street in central Oxford, England, and forms part of Merton College.
Oxford ( ) is a city in the South East region of England and the county town of Oxfordshire.
 With an estimated 2015 population of 168,270, it is the 52nd largest city in the United Kingdom, and one of the fastest growing and most ethnically diverse.
 The city is situated 57 mi from London, 69 mi from Bristol, 65 mi from both Southampton and Birmingham and 25 mi from Reading.
Dead Man's Walk (or Deadman's Walk) is a footpath running east–west in central Oxford, England, situated immediately to the south of Merton College and just outside the old city wall, with Corpus Christi College at the western end.
 To the north, Grove Walk connects with Merton Street through a gateway.
 Immediately to the south is Merton Field with Merton Walk connecting to the wide tree-lined Broad Walk, which runs parallel with Dead Man's Walk.
 Beyond that is Christ Church Meadow.