>> it was billed as one of the top-ten most luxurious buildings in the world. >> it had its own gym. its own pool. its own theater. >> reporter: they paid more than 4 million for their condo on the 50th floor. five years later, they received the troubling news, the high rise was not only sinking, it was also tilting, as illustrated in this now-infamous video. >> it was the very first time we did it. he got the marble out and said i am going to roll this and see what it does. it rolls about 10 feet out. slows to a stop. and then, turns around and starts rolling back and picks up speed as it goe...