Learn Spanish (Spain): Es el restaurante donde comimos el otro día. - It is the restaurant where we ate the other day.

Even though a restaurant is a physical location, we are not describing where it is located (for example, El restaurante está en Madrid). Instead, we are identifying what it is. For identifying people, places, or things, we always use the verb ser (which gives us Es).

Why doesn't the word donde have an accent mark over the 'o'?

In Spanish, question words only get accent marks when they are actually asking a direct or indirect question (like ¿Dónde está?). Here, donde connects the two parts of the sentence and just means "the place where," so it doesn't need an accent mark.

Could comimos also mean "we eat" in the present tense?

No, because comer is an -er verb. In the present tense, "we eat" is comemos. The ending -imos tells you it is definitely the past tense (preterite) "we ate." Only -ir verbs (like vivir) share the exact same form for both present and past tense (vivimos).

Why do we use the simple past tense (comimos) here instead of the imperfect past tense?

The phrase el otro día (the other day) refers to a specific, completed event that happened at a set point in the past. Because eating there was a single, finished action, Spanish uses the preterite (simple past) tense rather than the imperfect.