Kids & Co., a licensed day care facility with spots for 200 children, signed a 16-year lease for 20,247 square feet in the office building at 451 D St. in Boston.

The nine-story building totals 461,046 square feet in Boston’s Seaport District. In addition to the day care facility, the property’s other amenities include food service, fitness center with towel service, conference center and on-site parking. Kids & Co.’s space will also be equipped…