user: Question: How tall is the Anqing Bridge which opened prior to 2011?
Columns: ['Name', 'Height of bridge structure', 'Longest Span', 'Type', 'Opened', 'Location']
Types: ['text', 'text', 'text', 'text', 'real', 'text']
Sample row: ['Millau Viaduct', 'metres (ft)', 'metres (ft)', 'Cable-stayed', 2004.0, 'France - Millau']
SQL:

assistant: SELECT "Height of bridge structure" FROM "Table" WHERE "Opened" < 2011.0 AND "Name" = 'Anqing Bridge';