It is located on a mountain roughly outside of Bikini Bottom. The restaurant is made of wood and is covered in some snow. The top part has a sign with the words "Taco Haüs" written on a giant taco with a bratwurst sausage.
The inside of the restaurant has a photo booth, a cuckoo clock, and some stale chips, which are the items used to build the time machine.
Storyboard floor plan
Storyboard interior view
It is said to be an abandoned Mexican-German restaurant despite lights inside still being left on. The founder and employment there is so far unknown. SpongeBob, Plankton, and Karen once went into this abandoned restaurant to build a time machine and retrieve the secret formula.
Sausage (presumably a German bratwurst)
The word "haüs" means "house" in the German language. The full translation of the word is "Taco House."