(S (S (NP (BASENP (NNP UNESCO)) (PRN (COMMA ,) (NP (BASENP (DT the) (JJ cultural) (NN body)) (PP (IN of) (BASENP (DT the) (NNP United) (NNPS Nations)))) (COMMA ,))) (VP (VBD warned) (SBAR (IN that) (S (BASENP (DT the) (NN skyscraper)) (VP (PRN (COMMA ,) (SBAR (IN if) (FRAG (VP (VBN built)))) (COMMA ,)) (VP (MD may) (VP (VB endanger) (NP (BASENP (NNP St) (NNP Petersburg) (POS 's)) (BASENP (NN world) (NN heritage) (NN site) (NN status)))))))))) (PERIOD .))