Gunnerkrigg Court

Gunnerkrigg Court is (or was, before Agatha took possession of the town) an inn in Mechanicsburg which advertised.

Possibly relevant outside information
In fact, this is one of many shoutouts to other webcomics. Gunnerkrigg Court is a work with many similarities to the present history:
 * age: started April 2005, the same month Girl Genius became a web comic
 * format
 * one page published on Web MWF (since 2006; twice-weekly before that)
 * collected as graphic novels
 * protagonist
 * female student
 * parents dead or missing
 * extraordinary powers
 * story: mysteries slowly being revealed
 * setting: dark
 * overall excellence

Moreover, in January 2016, Professora Foglio announced Killer Robot’s (a third party) Legendary Showdown: Machines and Magic game had shipped. This game includes characters and artifacts from both works.