Question: the brandenburg gate in berlin marks what type of boundary
[{'answer': 'City gate', 'provenance': [{'wikipedia_id': '156604', 'title': 'Brandenburg Gate', 'start_paragraph_id': 1, 'start_character': 311, 'end_paragraph_id': 1, 'end_character': 320, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]