Building - one of those words that are difficult to pin down, because it can be countable (a building = budova) or uncountable (building = stavebníctvo), it can mean an activity (during the building of the new HDG line), it can be an adjective (a building worker, the building trade), or a gerund (people involved in building the line), or a participle (when they were building the line, or: pressure is building up).

Sometimes it can be replaced with "construct" (constructing, construction), like a construction worker, when they were constructing the line - but this word is more technical than "building", with more focus on bolting pieces of steel together into a structure (remember those old photos of the steeljacks high up on the skyscraper frames in New York?). So "a construction" is not the same as "a building". The technical term for the branch of study is "civil engineering", one of the faculties at the Technical Univerity in Košice.