Marlborough is a city in Massachusetts, United States. It is located in Middlesex County and is part of the larger Boston metropolitan area. The population of Marlborough is approximately 40,000 people. The city is known for its historic downtown area, which features a variety of shops, restaurants, and cultural attractions. Marlborough is also home to several high-tech companies and is a major center for biotechnology and photonics industries. The city offers a range of recreational opportunities, including parks, hiking trails, and sports facilities. Overall, Marlborough is a vibrant and diverse city with a mix of residential, commercial, and industrial areas.