"There are many big windows on the new building."
Translation:Az új épületen sok nagy ablak van.
Because, as always, what's in front of the verb gets emphasized. So, what you would be saying could be understood as "The many new windows are on the building (and not on the horse)", for example. Imagine it as an answer to the question "What has many windows?" Or "On what are many windows?"
But with a different emphasis you could make it work like the sentence above. Yet, it is unusual at best. Sounds a bit like "ta-daaa, the new building has many windows!"