to visit , this laboratory of laughter 
(ROOT (S (VP (TO to) (VP (VB visit) (, ,) (NP (NP (DT this) (NN laboratory)) (PP (IN of) (NP (NN laughter))))))))
(ROOT (S (VP (TO ) (VP (VB ) (, ) (NP (NP (DT ) (NN )) (PP (IN ) (NP (NN ))))))))