What is the best sound system you ever heard?

Not an electronic system, but the best sound I've ever heard was the Vienna Philharmonic Orchestra playing in the Musikverein  in Vienna. 

@elizabeth...Sadly, speaks to my failure to go anywhere.... My own.

Believe me, most of the systems set up during exhibitions will not outperform what you have carefully set up at home, components selected to your liking, possibly spent lots of time on room-tuning and so on. 

For me, its also my own system...before I moved house. (previous room was tuned during nearly 10 years of time, now have to start all over again). On the other hand, that's why I like this hobby....

It would certainly help one in developing a good sounding system to be able to listen to other systems, whether they were better or worse. But especially if they were better, you know, to give one a target to aim for. Compared to what? Stovepiping has its drawbacks. Tennis players oft comment they improve their game by playing better players.