Responding to its floodplain site, the original public library building spans Boulder Creek and offers glass-walled views of creek and greenway. The 53,000-square-foot 1992 addition along Arapahoe consists of a three-story sandstone cube fronted by a truncated, skewed glass cone over the doors. The dramatic entry previews the interior, including a children's library with an outdoor terrace. Lyons sandstone, laid in rough vertical ashlar courses, helps to unify the two strong, glassy contemporary designs, as does the glass-walled Boulder Creek bridge, which houses the library shop and coffee bar. Aquariums inside the library allow a closer look at some of the aquatic life in Boulder Creek.