http://apod.nasa.gov/apod/ap081220.html

Absolutely amazing. Newgrange is a passage tomb over 5000 years old (for comparason, Stonehenge wasn't built for another 1000 years after this) in Co. Meath, Ireland. On the winter solstice, the sun lines up perfectly, shining light directly down the passage, illuminating the central chamber. God, I love archaeology.