Every summer my wife and I are lucky enough to take student groups from the University of South Florida (and occasionally other schools) to Ireland for a three-week travel/study tour. Here's a shot of this year's group at Newgrange, the 5000-year-old site located north of Dublin. You get to walk deep into the building to an altar area. This is probably the oldest continuously roofed structure on Earth. It's amazing and I never get tired of visiting.