From a boathouse to one of the most beautiful libraries in the country

Frank Lloyd Wright continues to be one of the most influential architects today. But much of the architect’s design ethos was shaped by the great Louis Sullivan, who is often known as the “Father of Modernism.”

Yet the work of Sullivan was also shaped by another architect: Frank Furness of Philadelphia. At the early age of 17, Sullivan took on an apprenticeship at the office of Furness & Hewitt. Though brief, Furness managed to leave a lasting impression on the young designer, who would go onto describe Furness as someone who “made buildings out of his head.”

Furness, born on November 12, 1839, was a prolific architect. It’s estimated that he designed nearly 200 buildings, residences, churches, banks, and more between 1878 and 1906, but many of them have since met the wrecking ball or have been altered beyond recognition. Still, many of his showstoppers still remain in Philadelphia and the surrounding region, including these 10 fantastical works below.

This is by no means a complete list of Furness’s existing works, but they offer some of the best examples of his ornamental and whimsical style, plus evolution as a designer over the years. They’re listed in order of the date they were designed and built.

If you’re eager to check out more Frank Furness works, read about the massive, 42-room mansion he designed, which was put up for auction last year, or the brownstone that’s being redeveloped into multi-million-dollar condos.

Have another Furness favorite? Share your pick(s) in the comments.