The train line out to Kings Cross and Bondi Junction runs beneath the street, with Martin Place station situated towards the eastern end of the mall. Trains are not stopping at the station currently.
The street is often visited by tourists, especially this month with the erection of a large Christmas tree at its western end.
The Lindt cafe on the corner on Philip Street is directly opposite the Channel Seven studios, from which the network broadcasts its high-rating AM shows Sunrise and The Morning Show.
Channel 7's Martin Place studio staff unwittingly became siege central, with The Morning Show's Larry Emdur and Kylie Gillies cutting from regular programming to broadcast the chilling vision live.
Seven News' senior reporter Chris Reason was brought in to add commentary, while the rest of the Sydney news and current affairs staff were ordered to evacuate the building by NSW Police.
At 10.30am, the seriousness of the ISIS threat forced the remaining TV production staff to leave the premises, throwing to the network's Melbourne news crew, anchored by Nick Etchells and Laurel Irving.
TV executive producer Max Uechtriz tweeted confirmation of the terror scenario, with hostages forced to hold up the sinister black flag of the Islamic terror group.
Based on news staff eyewitness accounts, at least two suspects were identified walking around inside the cafe, one wearing an ISIS-tagged headband.
The Lindt cafe is a luxe space in a marble building, with high ceilings, gold trimmed furnishings and wall-to-wall chocolate displays.
Large bins of Lindt balls, in the colours of Christmas, have been placed just as you walk into the store.
- news.com.au