The basic Hebrew word for place is מָקוֹם, while the word site – אֲתַר – is borrowed from Aramaic, where it is the basic word for place. אתר is used in Modern Hebrew to refer to a site, including a website.
To build is לִבְנוֹת, an active-simple פָּעַל verb. While a building is a בִּנְיָן, the act of building or construction is בְּנִיָּה,
Thus, to refer a construction site in Hebrew, you’d use:
literally, a site of construction
And to say, this site is under construction, you’d say:
literally, the site is in construction