I was doing a lesson the other day(on another site).Its point was to teach that although estar is usually used for location, the location of an event was expressed using ser. I had read this before and all was well until I was doing the test for the lesson. One question was: "¿Donde esta la fiesta'" and the answer was: "La fiesta es a mi casa" or something like that. Shouldn't the question have been:"¿Donde es la Fiesta'"
ser and location of events
Last night I did the Ser v Estar lesson on this site.
It was excellant.
Steve, you are correct that estar is used for the location of objects, but in the case of intangible things, which occur rather than exist tangibly, the correct verb is ser. You can think of ser here being a substitute for tener lugar. Here is a discussion of this very question at WR:
Steve is going to be nominated as "error finder".
You are quite right: ¿Dónde es la fiesta?
We also say:
Estamos en fiesta, cuando se trata de las fiestas de un pueblo.