Question: where are the floating gardens of mexico city located
[{'answer': 'Lake Xochimilco', 'provenance': [{'wikipedia_id': '408595', 'title': 'Xochimilco', 'start_paragraph_id': 1, 'start_character': 233, 'end_paragraph_id': 1, 'end_character': 248, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]