What is the tallest building in the capital city of Spain?
{'directed': True, 'multigraph': False, 'graph': {}, 'nodes': [{'type': 'QUESTIONS_ENTITY', 'name_': 'Q29', 'id': 0, 'label': 'Spain'}, {'type': 'INTERNAL', 'name_': 'Q56787345', 'id': 1, 'label': 'Puerta de Europa II'}, {'type': 'ANSWER_CANDIDATE_ENTITY', 'name_': 'Q1141262', 'id': 2, 'label': 'Gate of Europe'}], 'links': [{'name_': 'P17', 'source': 1, 'target': 0, 'label': 'country'}, {'name_': 'P361', 'source': 1, 'target': 2, 'label': 'part of'}]}