The most beautiful place I've seen so far was Jiuzhaigou in Sichuan, China. That was in 2017, months before the place was severely affected by a huge earthquake.
We took a bus to the top of a mountain in the national park and then hiked all the way down through lush forests. For a good portion of the hike, we didn't meet a single soul and felt like the last people on Earth. I felt like I saw everything nature has to offer in a single day: tall, lush trees; majestic waterfalls; shimmering lakes in every imaginable shade of blue; exotic birds; rivers that had two different colours (yellow and blue-ish) because of different sediments.
But the most stunning view for me was the view to the mountaintop near our hostel. It was like a postcard or a painting. Underneath the bright blue sky, you could see light grey mountaintops covered in snow. At the foot of the mountains, there were lush meadows, yaks chilling on them, wild flowers growing everywhere. And right beneath those, seemingly endleelss fields of lavender. It was the most beautiful thing I've ever seen!
I'm with you on team "O holy night", my favourite version is Andy Williams', closely followed by Perry Como's!