Ireland is a magical place full of megalithic tombs. Some say that these tombs were probably built before the arrival of the Celts, who called them fairy mounds and believed that the spirits of ancient people–bold heroes and brave maidens–lived there. The Celtic creator gods, the Tuatha de Danann, were known to be extraordinarily good at building things, and perhaps it was they who constructed the tombs dotting the countryside.

Eventually, the spirits inhabiting the fairy mounds transformed into the little people of later Irish legends–leprechauns and fairies and brownies, whose spirits are said to haunt the land.

Many of these tombs are called passage tombs because they contain passages leading to burial chambers underneath the mound. The walls of the passage and chamber are made of rock that is elaborately carved.

Court tombs, or cairns, have an open, roofless courtyard in front leading into two, three, or four chambers at back. Archaeologists have found human remains in them but think they might originally have been built as temples. They tend to be evenly distributed about three miles apart instead of clustered like modern graves; generally structures that are spaced

like that are places of worship, but there’s no way to tell for sure how the people of ancient Ireland used them. Court cairns are considered the oldest types of monuments in Ireland. They date from around 4000 BC and the most well-known are found at Creeveykeel and Deerpark in Co Sligo, Rathlackan in Co Mayo.

Wedge tombs also occur primarily in the northern part of Ireland. These tombs have stone walls and roofs; the roof gets lower and the passage narrower as one goes into the tomb, hence the name wedge. Most of them face west or southwest, toward the setting sun.

Wedge tombs are numerous; there are about 500 of them all over the northern part of the country, although some can be found on Ireland’s eastern coastline. Human remains have been found in the tombs that have been excavated, along with some pottery, which suggests they were made toward the end of the Neolithic period.

Labbacalle (“Hag’s Bed”), in County Cork, is an excellent wedge tomb. It got its strange name because it contained the skeleton of a headless woman when it was first opened.

Portal tombs, also called dolmens, consist of several large upright stones topped by a giant capstone. Putting these rocks in place must have been a stupendous effort–some capstones weigh as much as 100 tons. These dolmens were originally surrounded by mounds of earth, and people were buried inside them. A giant dolmen at Poulnabrone, County Clare, had more than 20 people buried in it over a 600-year period; this might mean that only royalty was buried there. There are dolmens all over Ireland, as well as in Wales and Cornwall. The Kilclooney More dolmen in County Donegal is particularly cool–its capstone is almost 14-feet long.

Some of the most spectacular archaeological sites from the Neolithic period are in the Boyne Valley in County Meath. These sites are called Brú na Bóinne which means palace of the Boyne. They consist of large stone tombs built around 3200 BCE, several centuries before the great pyramids of Egypt. The three main components of this site are Newgrange, Knowth, and Dowth.

People have known about these tombs for centuries; Vikings plundered them, while Victorians hunted treasures there and carved their initials on the walls. The sites gradually deteriorated and were even quarried at one point.

The tombs at Newgrange are built inside a huge, grassy mound of earth. The stones at the entrance and some of the stones holding the tomb together are elaborately carved with spirals. The stones that were used were not local; some of them came from Wicklow, 50 miles away, and others from northern Ireland. This indicates that whoever built them was very organized.

The Newgrange tomb might have been surrounded by a ring of giant stones, though only 12 of these now remain. Inside the mound is a long passageway leading to a subterranean burial chamber. Inside the chamber are three recesses for holding remains. The front door of Newgrange is a solar observatory.

When Newgrange was first excavated by experts, archaeologists found the remains of at list three cremated bodies and some human bones. Offerings of jewelry were probably once there as well, but these were stolen long ago.

No one knows exactly why these mounds were built. They might have been burial places for kings; ancient legends certainly suggest that as a possibility. Or they might have served as calendars. Many megalithic sites are constructed to catch the sun at particular times of the year, and they are astonishingly accurate!

Newgrange is the best-known example of this. Every year during the winter solstice (December 19-23), the rising sun shines through a slit over the entrance and lights up the burial chamber for 17 minutes. At the time the tomb was built, the sunlight would have shone directly onto a spiral design carved into the wall.

Similar phenomena happen at other megalithic sites. The light of the setting sun at winter solstice illuminates one of the chambers inside Dowth. At Knowth, the eastern passage seems to have been designed to catch the rising sun of the spring and autumn equinoxes, while the western passage might have caught the setting sun on those same days.

The River Boyne, which flows past these mound tombs, has long been very important spiritually to the Irish people. Legend says that the first occupant of Newgrange was named Elcmar. His wife was Boann, the spirit of the river.