Question: The Imperial Arcade opened in 1891 on the site now occupied by a shopping centre operated by what company?

Context paragraphs:
Rivonia Square: Rivonia Square is the previous name of a shopping centre, including shops, the post office, a fitness centre and restaurants, along a thoroughfare called Rivonia Boulevard in Rivonia, Johannesburg.  Late in 2012 the centre was renamed 'Oriental City'.  It includes the area occupied by the first shopping centre built on the site – the Cloisters Shopping Centre.  The Cloisters took its name from the Rivonia Convent, a closed order of Carmelite nuns, which originally existed on the site.

Cairns Central: Cairns Central Shopping Centre in north Queensland, Australia is Cairns' biggest shopping centre.  The centre was opened in late 1997 and is the second multi-story shopping centre in northern Queensland.  The shopping centre is built over the Cairns Railway Station, which is incorporated with the centre.  Pedestrian access to the station is through the car park on the bottom floor, or a pedestrian walkway on the second floor.  Construction of the shopping centre was delayed temporarily due to damage suffered from Tropical Cyclone Justin in early 1997.

Joseph Thomas Burton-Gibbs: Joseph Thomas Burton-Gibbs was one of Sydney's "oldest business identities".  Born in Derby, England, Burton-Gibbs emigrated to Melbourne in 1853 aboard the ship "Indian Queen".  In 1866 he helped establish a printing and publishing house, Clarson, Shallard & Co, with partners Joseph Shallard, Alfred Henry Massina and William Clarson.  In 1862 he moved to Sydney to open a branch of the company at 207 Pitt Street.  Although the original partnership was dissolved in 1866, Burton-Gibbs continued his partnership with Joseph Shallard, trading as Gibbs, Shallard and Co, which went on to become a leading printer and publisher in the city.  One well-known publication was the "Illustrated Sydney News".  In 1889, he became a founding director of the Imperial Arcade Company Ltd which developed the Imperial Arcade, Sydney.

Athlone Town Centre: Athlone Towncentre is a shopping centre located in Athlone, County Westmeath, Ireland.  The shopping centre is the largest shopping centre in the Irish midlands with over 140,000 sq meters of retail space consisting of 60 high end retail shops.  The Shopping centre is located in the heart of Athlone town enclosing a site on Dublin Gate Street and Gleeson Street.  The Shopping Centre opened in 2007.  The 4 star Sheraton Hotel adjoins the site and consists of 161 beds.  Anchor tenants include Marks and Spencer, River Island, Tommy Hilfiger, Topshop, Next, H&M, Monsoon amongst many more.

Westfield Sydney: Westfield Sydney is a shopping centre operated by Scentre Group and located beneath the Sydney Tower in the Sydney central business district.  It is located on Pitt Street Mall and is adjacent to the Mid City Centre, The Strand Arcade and Stockland Glasshouse.

Lavington Square Shopping Centre: Lavington Square Shopping Centre opened in 1979 in the Albury suburb of Lavington, New South Wales, Australia.  Since opening the shopping centre has undergone several upgrades and name changes the most major upgrades to the centre were done after Centro bought the shopping centre in 1994.  The shopping centre currently has 57 specialty retailers and 3 major retailers including Woolworths, BIG W and Aldi.  The shopping centre also houses the lavington Australia Post branch for the post code of 2641.  In 2013, the centre's revenue was $116 million.

Imperial Arcade, Sydney: The Imperial Arcade was a commercial building in Sydney, Australia, designed by prominent Sydney architect Thomas Rowe opened in 1891 on the site now occupied by Westfield Sydney.

Piccadilly Theatre and Arcade: The Piccadilly Cinema Centre (formerly Piccadilly Theatre) and Piccadilly Arcade are located at 700-704 Hay Street, Perth, Western Australia.  It is an art deco style cinema and shopping arcade, designed by architect William T. Leighton for mining entrepreneur Claude de Bernales.  The theatre and arcade opened in 1938, with the arcade connecting Hay Street through to Murray Street.  In 1984 the theatre and arcade underwent a significant refurbishment, with the refurbishment winning an architectural award from the Royal Australian Institute of Architecture (WA Chapter) in 1986.  The theatre and arcade are classified by the National Trust of Australia and are included on the State Heritage Register.  The Piccadilly Cinema was the last remaining operating cinema in the Perth central business district before its closure in 2013.

Bluewater (shopping centre): Bluewater Shopping Centre (commonly referred to as Bluewater) is an out-of-town shopping centre in Stone (postally Greenhithe), Kent, England, outside the M25 Orbital motorway, 17.8 mi east south-east of London's centre.  Opened on 16 March 1999 in a former chalk quarry after ten years of building works, the site including car parks occupies 240 acres and has a sales floor area of 154,000 m (1,600,000 ft) over three levels, making it the fourth-largest shopping centre in the UK (after the MetroCentre, Trafford Centre and Westfield Stratford City).  Elsewhere in Europe only Istanbul's Cevahir Mall and Vienna's (Vösendorf) Shopping City Süd are bigger.  The floor plan is a triangular shape with 330 stores, including 3 anchors, 40 cafés and restaurants, and a 13-screen cinema.  The centre employs 7,000 people and serves over 27 million visitors a year.  A main rival is the Lakeside Shopping Centre and its two retail parks by road 8 mi away in West Thurrock, Essex, just across the River Thames or 3.2 mi point-to-point.

Elmvale Acres Shopping Centre: Elmvale Acres Shopping Centre is an open-air mall located in the Elmvale Acres neighbourhood of Ottawa, Ontario, Canada.  It opened in 1961, making it one of the oldest shopping centres in the city.  The mall is just a short 10-minute drive south of St. Laurent Shopping Centre.  The shopping centre is also just a 3-minute drive from the Canadian Museum of Science of Technology (closed until 2017).  The Smythe Medical Centre is located just across from the north end of the mall.  The mall is bounded by Smythe Road to the north, Othello Avenue to the west, Russell Road to the east, and St. Laurent Boulevard to the south.  The shopping centre has approximately 60 shops and services including Dollar Plus, LCBO, Loblaws, Rexall Pharma Plus, Royal Bank, The Beer Store, and the Ottawa Public Library.  The shopping centre is adjacent to the Elmvale Transit Station.  The size of the total complex is 147,332 square feet.  The shopping centre is currently owned by Rio-Can Real Estate Investment Trust.

Supporting paragraphs: Imperial Arcade, Sydney Westfield Sydney
Answer: Scentre Group