Complex sentence: The Central Library, which used remodeled space that formerly housed a Bay outlet, which not only allowed for an economical expansion of the branch but also enjoyed a more central location in the city's downtown core.
Split into simpler sentences: The Central Library was built in a remodeled space that formerly housed a Bay outlet. This not only allowed for an economical expansion of the branch but also offered the library a more central location in the city's downtown core.