Question: are monchengladbach and dortmund rivals?
Answer: Based on membership, Borussia Mönchengladbach is the fifth largest club in Germany, with over 75,000 members. The club's main rivals are FC Köln, against whom they contest the Rheinland Derby. Secondary rivals include Borussia Dortmund, Fortuna Düsseldorf, and Bayer Leverkusen.