Newgrange is a prehistoric megalithic tomb dating back to about 3200 BC, making it older than both Stonehenge and the Egyptian pyramids. It consists of a large circular mound with an inner stone passageway and chambers. The entrance and passageway is aligned with the rising sun on the winter solstice, such that the sunlight for a short moment reach the inner chamber. Newgrange is a part the UNESCO World Heritage site of Brú na Bóinne Complex, which also include the neighbouring similar sites of Knowth and Dowth. The Brú na Bóinne Complex is considered to be Europe's largest and most important concentration of prehistoric megalithic art. Of the three sites, Newgrange is the only site where you can get into the chamber. A guided tour is necessary and starts from the Brú na Bóinne visitor centre. Tickets can sell out fast, so book ahead.
Scandinavia is normally known for its Vikings, but long before, in the Bronze Age (about three thousands years ago), the region was home to hunting communities that carved their spiritual world and daily life into flat rocks. To this day, these mystical figures, farmers, animals, boats and patterns are still easily seen in Tanum, one of the prime areas for these Nordic rock carvings, and consitute a peek into an ancient world. Their numbers are remarkably high here and they are still half hidden in the pine forest as they probably have been for millenniums. There are four main sites in Tanum, Vitlycke (right next to the museum), Fossum, Aspebjerget, and Litsleby, all within a few minutes drive from each other.
Nemrut is a mountain in eastern Turkey. So far nothing special, but in the first century B.C. king Antiochus build something mind blowing on the dusty summit. Huge statues of up to 9 meters tall of himself and a number of Greek, Armenian and Persian gods, and to top it of, an artificial peak of stone rubbles which is believed to be his tomb (but nobody knows). Today the statues are broken into pieces that are scattered on the mountain top, but the giant heads are still gazing proudly over the plateau below.