To reduce the confusion with the geometric meaning of square I suggest adding an additional on hover translation of 'town square' for náměstí. Town square is what is meant when the shortened version 'square' is used in English. 'The big square' without context in English would suggest primarily the geometric meaning.
Yep, there is no "a" or "the" in Czech, but when you would say "THE big square" it would suggest that you are talking about some specific square you mentioned earlier in the context probably. In Czech, that could be expressed as "TO velké náměstí", where TO is literally like a word expression for pointing at something specific. Example: "Which square do you mean? THE big square in the center?" "Které náměstí myslíš? TO velké náměstí v centru?"
It is true that Czech does not use articles like the English "a" and "the." So it puts demonstrative pronouns to use for that purpose.
The course consistently uses "ten" (in its various genders and cases) as EITHER "the" or "that." Sometimes in our translations we can pick one or the other based on context. When there is no context -- which is most of the time... -- either one seems to be accepted.
"Ten (etc.)" is never translated here (anywhere?) as "this." "This" could be either "tento" or "tenhle" (with the appropriate gender/case changes), the latter being less formal.
As English is an analytical language and Czech is synthetic language, I wrote it as: "It is the large square" But I'm always using Czech "to" as the English "it", so it's nonsense to support articles when Czech doesn't have them. Literally it says "It/that big/large square/plaza" but no way "the". We're trying to learn Czech, so I recommend a literal translation and a practical translation. Practical is what was shown. Literal is what I wrote previously in this post. I feel it gives more appreciation for the language and how to think in it as well.
no, czech is not russian, and "It is the large square." would require that a form of "be" be inserted, and i would actually suggest you'd even need a second "to" because otherwise why didn't you just say "It is a large square."? so your proposal corresponds to To je to velké náměstí. maybe you can use that last example to appreciate that there is more than just one kind of "to" in czech.