"This is the Slovak village that was in Moravia back then."

Translation: Toto je ta slovenská vesnice, jež tehdy byla na Moravě.

[walkinwolk]

Please explain why I must use “toto” instead of “tato”. I thought the first part of “this” had to match the gender of the subject it describes. Would “tahle” also be incorrect?

[VladaFu]

No, this is a recurring pattern. It is the same as "To je...". Like in English "It is...".

It is some unidentified "to", just learn it as a pattern.

[walkinwolk]

Could I say “To je moje zena”?

[VladaFu]

You have to. Unless you are pointing into a group of ladies to one of them and saying "Ta je moje žena" as opposed to those that are not.

[purpoze]

This one is tricky. We could use: ’’Tohle je slovenská vesnice, která byla předtím na Moravě.’’ and it would be OK if there was no historical timeframe. Even more natural would be: ’’Tohle je slovenská vesnice, která byla kdysi na Moravě’’ but that is not exactly the same since ’’kdysi’’ is more vague and more like ’’back in the day’’.