Ernst Haeckel was the most influential biologist in Germany in the late nineteenth century, and he spent most of his working life at the University of Jena. His home, the Villa Medusa, now operates as a museum dedicated to his life and work, containing his original study, his scientific instruments, and a large collection of his natural history specimens and drawings.
Haeckel was a complex figure — a brilliant systematiser of Darwin's ideas, an extraordinary illustrator, and also the originator of ideas about "recapitulation theory" that were later misappropriated. The museum presents all of this without flinching, and the house itself — cluttered with curiosities, books, and specimens — gives a vivid sense of Victorian scientific domesticity. It's a ten-minute walk south from the university centre.