During Klara's Monday evening broadcast this week, a message from Daithi said he was testing transmissions from Newgrange. I'd heard the name, but didn't know anything about it, so I looked it up on Wikipedia. It's a restored Neolithic passage tomb that's 5,000 years old, with the passage aligned to admit the sun down a long passage into the interior on the morning of the Winter Solstice.
One of the Wikipedia links was to a video about the 2007 Solstice. It's an hour long and very informative. The weather for that day was perfect, if a bit cold for the presenters, at just about freezing (0C, 32F). It was interesting to watch as the sun rose and several minutes later the passageway was illiminated by it. 5,000 years ago, the passageway would've been lit right at sunrise, but the Earth's tilt has changed, so that now happens about four minutes later.
Here's that link: http://www.heritageireland.ie/en/Solstice2007/
The Wikipedia link to Newgrange: http://en.wikipedia.org/wiki/Newgrange