I haven't tried opium, but cannot imagine that Opium smells much like an opium den; and it is impossible to guess at what the millennium will smell like.
( ( ( ( ( I ( ( ( ( ( have n't ) ( tried opium ) ) , ) but ) ( ( can not ) ( imagine ( that ( Opium ( ( smells much ) ( like ( an ( opium den ) ) ) ) ) ) ) ) ) ) ; ) and ) ( it ( is ( impossible ( to ( guess ( at ( what ( ( the ( millennium ( will smell ) ) ) like ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (PRP I)) (VP (VP (VBP have) (RB n't) (VP (VBN tried) (NP (NN opium)))) (, ,) (CC but) (VP (MD can) (RB not) (VP (VB imagine) (SBAR (IN that) (S (NP (NNP Opium)) (VP (VBZ smells) (NP (RB much)) (PP (IN like) (NP (DT an) (NN opium) (NN den)))))))))) (: ;) (CC and) (S (NP (PRP it)) (VP (VBZ is) (ADJP (JJ impossible) (S (VP (TO to) (VP (VB guess) (PP (IN at) (SBAR (WHNP (WP what)) (S (NP (DT the) (JJ millennium) (NN will) (NN smell)) (VP (VBP like))))))))))) (. .)))
I've used the drug opium, and know that the perfume Opium smells like it. 
( I ( ( ( ( ( 've ( used ( the ( drug opium ) ) ) ) , ) and ) ( know ( that ( ( the ( perfume Opium ) ) ( smells ( like it ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP I)) (VP (VP (VBP 've) (VP (VBN used) (NP (DT the) (NN drug) (NN opium)))) (, ,) (CC and) (VP (VBP know) (SBAR (IN that) (S (NP (DT the) (NN perfume) (NN Opium)) (VP (VBZ smells) (PP (IN like) (NP (PRP it)))))))) (. .)))