Sheraton in Lisbon
I booked a 3 night stay for my wife after her conference was over in Lisbon few years ago. She still raves about this hotel whenever we go to another 5 star property:
"Lisbon - Sheraton, Incredible Design - ultra modern - almost like a W. Great buffet breakfast. Cool rooftop bar (indoor). Nice outdoor pool and gift for plats" (as mentioned by another poster about this hotel)