Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_1688 ( "Province" text, "Provincial capital" text, "Largest city" text, "Area (km 2 )" real, "Population (2013)" real )

### Question ###
what is the largest city where the population is 6620100?

### Accurate SQL ###

SELECT "Largest city" FROM table_1688 WHERE "Population (2013)" = '6620100'