Casa de Santo Domingo
Santo Domingo is a monastery complex that was in ruins a decade or so ago. Since then, it's been partially excavated, placed in a state of suspended animation, and then turned into a 5-star hotel and museum complex. The effect is stunning: gorgeous modern architecture fused with (and built on top of) ruined walls and courtyards from a time gone past. On the surface this might sound like pure capitalism devouring the country's heritage, but it has been done with great respect for the site and the best intentions. I've never seen anything like it.