Ser vs Estar sentence

[Hiperbólico]

¡Hola! I was doing an online activity for class. A sentence was given, and I had to fill in the blank with the appropriate conjugation in simple present. Here's one I don't understand.

La fiesta de cumpleaños ____________ en la casa de Marta.

I thought it should be está, since it seems to concern location which is always estar. According to the activity, it needs es for ser, but I don't see how.

¿Alguién puede explicar esto?

[AngelicaDeAlquezar]

Unless there is someone with a better explanation for this, I think it's because a party is not a person, an object or an animal that can be moved from one place to another and still be what it originally was. It is rather an activity or a situation that mostly depends on the place where it can be held.
So you think in terms of the identity of the thing, which in this case is an activity, so we use the verb "ser".

- ¿Dónde es la reunión?
- La junta será en la oficina del jefe.
- El baile de graduación va a ser en el gimnasio de la escuela.
- El partido es en el Estadio Azteca.
- ¿Sabes dónde fue el último concierto de Madonna?

[wrholt]

The location of events is always with ser; the location of everything else is always with estar.

El concierto es en el auditorio = the concert (performance = event) is in the auditorium.
El concierto está en la mesa = the concerto (musical score = non-event) is on the table.

[Hiperbólico]

Escrito originalmente por AngelicaDeAlquezar

Unless there is someone with a better explanation for this, I think it's because a party is not a person, an object or an animal that can be moved from one place to another and still be what it originally was. It is rather an activity or a situation that mostly depends on the place where it can be held.

Makes sense to me, and it also ties into what wrholt said i.e. the nature of them being events. Thanks, both of you especially for the examples. They really help.