The Boston Public Library - designed by McKim, Mead & White in 1895 - is know for it's traditional architecture and stately interiors in the original Renaissance style McKim Building.
The reading room:
In 1972, a new addition designed by modernist architect Philip Johnson (of the Glass House fame) was added behind the original building.
I will say that the interiors were just dreadful in this building. I lived in Boston in the '80's (so it was still relatively new) but going into this building, which houses the main circulating collection and is the main entrance for most library goers, was pretty depressing. I just remember everything being so brown and dingy. One can imagine how uninspiring this space would be for children. So it's a good thing that the first phase of a large ongoing remodel of the Johnson building includes the construction of a new children's room, a teen space and community reading area. These spaces have just opened and are pretty great.
I love the lion cub above which seems to be a play on the stately grand lions in the staircase of the original library building.
These spaces are fresh and colorful, with lots of seating to cuddle up in and lots of visual appeal to spark the imagination.