CREATE TABLE table_6209 ("Date" TEXT, "Course" TEXT, "Distance" TEXT, "Type" TEXT, "Winner" TEXT)

Which course has a flat stage on 4 September?
SELECT "Course" FROM table_6209 WHERE "Type" = 'flat stage' AND "Date" = '4 september'
SELECT "Course" FROM "table_6209" WHERE "Date" = '4 september' AND "Type" = 'flat stage'