The Research Triangle Park
The park is home to over 190 companies employing 50,000 workers and 10,000 contractors, including the second largest IBM operation in the world. The park hosts one of GlaxoSmithKline's largest R&D centers with approximately 5,000 employees. Cisco Systems' campus in RTP, with approximately 4,000 employees.
For a complete list of companies in RTP reference this site.