Maple Leaf Gardens, Madison Square Garden, Boston Garden, The Montreal Forum, Chicago Stadium, and The Detroit Olympia.
These arenas housed the teams known as "The Original Six." They are hallowed halls that are spoken about in tones that always acknowledge their history. Their fates are deemed travesties, as teams moved onto new arenas that have all the modern (at the time anyways in some cases) toys and bells and whistles that every team wanted, and that could serve multiple uses -- as their owners wanted.
What happened to these old buildings once they were of no use?