Newgrange

Just north of Dublin is a VERY old passage tomb. It is 1,000 years older than Stonehenge and the Great Pyramids of Giza. It is the oldest domed roof structure ever discovered. It was designed so the rising sun on the Winter Solstice shines deep inside the tomb and lights up the back corners. The waiting list to see this is 10 years long and over 40,000 people apply for the lottery every year. Maybe 20 people (and that would be incredibly tight) would fit inside at any given time.