Thousands of federal employees work at the headquarters for the United States Patent and Trademark Office, located near the King Street Metro. School and group tours are welcome at the National Inventors Hall of Fame and Museum, located in the atrium of the Madison Building here. The museum includes a theater, portrait gallery and gift shop. The museum is open 9am - 5pm weekdays and noon - 5pm Saturdays. Tours are Mondays from 2pm - 4pm and Fridays 10am - noon. Admission is free. The space is available for events but only to specific groups.