For a moment I thought this thread was in Philosophy & Spirituality, but it's amongst you trippers... some great answers. From Asian women to toad tennis balls to Jessica Alba's anus. 
Visually I love sunsets on a partly cloudy day anywhere near the sea on acid. It's the only experience I can remember in my life where I almost wept just from the sheer beauty of something.
As for a "thing"... well love and women have already been suggested so in an effort to be original, my answer is hope. Which I'm surprised no one else has said... someone did say the present moment which is almost the opposite and in itself, a very beautiful thing.
Yet the present moment is for our existence, who we are and what we are doing. We can appreciate in the present moment but we don't build our dreams in it. While it's arguable whether animals have the capacity to hope as humans define the word, it's within the context of humanity that I find it the most beautiful.
Hope alone can build a wall so long that it's visible from space, and centuries later put man up there to see it. Empires fall, nations rise, wars end and entire societies are freed from the tyrannies of persecution by race, color or religion because of man's capacity to hope.
On an individual level, our ability to set goals, sometimes seemingly impossible or impossibly distant is what makes every proceeding day worth waking up for. Occasionally, humans even achieve dreams on the back of hopes that span generations.
Sure you need other things to go right, but without hope none of it would have been started or worked towards in the first place.

Visually I love sunsets on a partly cloudy day anywhere near the sea on acid. It's the only experience I can remember in my life where I almost wept just from the sheer beauty of something.
As for a "thing"... well love and women have already been suggested so in an effort to be original, my answer is hope. Which I'm surprised no one else has said... someone did say the present moment which is almost the opposite and in itself, a very beautiful thing.
Yet the present moment is for our existence, who we are and what we are doing. We can appreciate in the present moment but we don't build our dreams in it. While it's arguable whether animals have the capacity to hope as humans define the word, it's within the context of humanity that I find it the most beautiful.
Hope alone can build a wall so long that it's visible from space, and centuries later put man up there to see it. Empires fall, nations rise, wars end and entire societies are freed from the tyrannies of persecution by race, color or religion because of man's capacity to hope.
On an individual level, our ability to set goals, sometimes seemingly impossible or impossibly distant is what makes every proceeding day worth waking up for. Occasionally, humans even achieve dreams on the back of hopes that span generations.
Sure you need other things to go right, but without hope none of it would have been started or worked towards in the first place.