Stained glass window in in Sydney Town Hall, designed by Lucien Henry symbolising Australia. Photo by Paul Paterson, Courtesy City of Sydney Council.

It's on again this Sunday, 6 November! Sydney Open is your chance to be a sticky beak and see some of Sydney's most historic, striking and modern commercial buildings, along with our most beloved public buildings. Sydney Town Hall will be open. This year we are opening the Lord Mayor's formal office in the Town Hall, a space only a privileged few usually get to see, along with the Lord Mayor's reception room, set up for a banquet. Of course, the Centennial Hall is a highlight, particularly with concerts on the Grand Organ; and the Lucien Henry stained glass windows. And you can say hello to me - I'll be pointing out some of the artefacts associated with the burial ground that was on the site before the Town Hall was built. Another favourite of mine is the modernist AMP Building at Circular Quay. The rooftop terrace is open so take in an exclusive view - this was the first building to break through the 112 foot building height limit and once towered over low-rise Sydney. Do the modernist double, and visit the Harry Seidler designed Australia Square as well. New to the building list this year is the Macquarie Group at No.1 Martin Place. This is the General Post Office site and the modern office block associated with Macquarie Group. A groovy new atrium with an Escher-like staircase is a recent addition promoting connection and collaboration. The Calyx only opened in June 2016 and is another newbie on the Sydney Open list. It's a modern extension of the palm house in the Royal Botanic Garden. Back to some really old buildings and some old artefacts. One of Sydney's best kept secrets and creepiest museum is open - the Lucy Osburn-Nightingale Museum at the Sydney Hospital. It has specimens of all types of diseases. The Big Dig archaeology site in the Rocks and the youth hostel that has been built over the site is open as well. This is another great building with a rooftop terrace. And while we're exploring rooftop terraces, you may as well also take a peek at Hong Kong House on Druitt Street. Its rooftop balcony has a unique view of the domes of the Queen Victoria Building.  This is a ticketed event - you need to pre-purchase your ticket ($49 for a general ticket. Concessions available.)

Alfred Street, Circular Quay 1962, City of Sydney Archives (NSCA CRS 48/2877)

Lisa's top 5 roof top and views: AMP Building The Big Dig & YHA Hong Kong House EY Centre (levels 27 & 28) Two International Towers, Barangaroo (Level 35, Level 36, the Skyrise Level 41 - top floor) And don't worry if you can't get along this Sunday, the Dictionary of Sydney has lots of great images and information about many of these historic buildings so click on the links to go through to the Dictionary and you can explore at your leisure! Listen to the Lisa & Nic here and tune in to 2SER Breakfast with Nic Healey on 107.3 every Wednesday morning at 8:15-8:20 am to hear more from the Dictionary of Sydney.  Listen now