Basel is a city in Switzerland.
Circa 1520, Bombastus' workshop was located in the city. There, he lived and worked alongside his assistant Maria Amiel.
In 1520, the Assassin Giovanni Borgia visited Bombastus in Basel, in order to show him a Crystal Skull he had recovered from Tenochtitlan, México.
Bombastus' workshop was where he kept the first half of the Book, and was also where he created the Philosopher's Stone.