The annual event kicks-off on 13 and 14 September, and will offer access to venues normally firmly closed to the public.
Last year over 48,000 people took the opportunity to visit architectural marvels across the Province, free of charge.
NI Environment Minister Sammy Wilson visited just one of 240 landmarks - Belfast's Stranmillis College - to launch the event.
The Minister toured the site with renowned historian Dr Eamon Phoenix, and learned of the long-standing institute's hidden history.
Mr Wilson said: "As someone who trained at Stranmillis College to be a teacher, it has been fascinating to learn today about the history of the site. In many ways, this is a fine example of what European Heritage Open Days are all about.
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"Some of us have been lucky enough to have had access to the buildings as students or as staff.
"However we have not had the opportunity to simply stop, explore and appreciate, not just the history and architectural splendour of the main college building, but marvel at the hidden gem - Stranmillis House just behind it."
The minister paid tribute to all those who make the event possible.
"Our colleagues in Europe are very appreciative of the efforts that we have made to increase our numbers over the years from 12,500 visits in 1997 to a staggering 48,000 last year.
"European Heritage Open Days is the biggest outreach event organised by Northern Ireland Environment Agency (NIEA) and is a celebration of our common European heritage and the diversity of individual member sites.
"We are all very grateful to the owners and the custodians of buildings who open their doors to provide us with a rare opportunity to see inside.
"I would urge members of the public to grab this opportunity to see the best that Northern Ireland has to offer," added Mr Wilson.
Other attractions on offer include Benvarden Estate in Co Antrim, Loughgall Estate in Co Armagh, Portaferry Presbyterian Church in Co Down, Portora Royal School in Co Fermanagh, the Foyle Valley Railway Museum in Co Londonderry and Holy Hill House in Co Tyrone.
Brochures detailing all of the properties and events are available from libraries, tourist information centres and other outlets across Northern Ireland.
(PR/JM)
