This is not a run-on sentence. It is not formed from two sentences that have been run together without appropriate punctuation.
At the Morbid Anatomy Museum in Brooklyn, students can take taxidermy workshops in which they learn how to skin and stuff dead mice.
Is this a run-on sentence?
At the Morbid Anatomy Museum in Brooklyn, students can take taxidermy workshops in which they learn how to skin and stuff dead mice.
A: no
B: yes