A roofbox is a specially contrived opening above a doorway, usually built for some astronomical significant event.

The term was coined by Professor Michael O’Kelly during his excavation of the Newgrange

Newgrange

Newgrange is a prehistoric monument located in County Meath, on the eastern side of Ireland, about one kilometre north of the River Boyne. It was built around 3200 BC , during the Neolithic period...

 passage cairn, at Brú Na Bóinne

Brú na Bóinne

is a World Heritage Site in County Meath, Ireland and is the largest and one of the most important prehistoric megalithic sites in Europe.-The site:...

, Ireland.

The roofbox was built directly above the entrance door to the passage. The passage and chamber were specifically aligned with the rising sun of the mornings around the mid-winter solstice in December. The 17 metre passage rises in elevation as it leads to the chamber.

The chamber floor, the roofbox and the local horizon are on a single plane and so as the sun's morning rays penetrate the roofbox, they illuminate the chamber floor for a maximum of 17 minutes (weather depending).

A roofbox is also found in Cairn G of the Carrowkeel Megalithic Cemetery

Carrowkeel Megalithic Cemetery

Carrowkeel is a Neolithic passage tomb cemetery in the south of County Sligo, near Boyle, County Roscommon. An Cheathrú Chaol in Irish means 'the Narrow Quarter'. Circumstantial Carbon 14 dating places the tombs at between 5400 and 5100 years old, so that they predate the Pyramids on Egypt's Giza...

.