CREATE TABLE table_27233 ("Week" FLOAT, "Date" TEXT, "Kickoff" TEXT, "Opponent" TEXT, "Final score" TEXT, "Team record" TEXT, "Game site" TEXT, "Attendance" FLOAT)

What opponents played Waldstadion in a game?
SELECT "Opponent" FROM table_27233 WHERE "Game site" = 'Waldstadion'
SELECT "Opponent" FROM "table_27233" WHERE "Game site" = 'Waldstadion'