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_1140090_6 (circuit VARCHAR, winning_driver VARCHAR)

### Question ###
What circuit did Clay Regazzoni win?

### Accurate SQL ###

SELECT circuit FROM table_1140090_6 WHERE winning_driver = "Clay Regazzoni"