CREATE TABLE table_11815 ("Home team" TEXT, "Home team score" TEXT, "Away team" TEXT, "Away team score" TEXT, "Venue" TEXT, "Crowd" FLOAT, "Date" TEXT)

Where did Essendon play as the away team?
SELECT "Venue" FROM table_11815 WHERE "Away team" = 'essendon'
SELECT "Venue" FROM "table_11815" WHERE "Away team" = 'essendon'