mon·u·men·tal / ˌmänyəˈmentl/ • adj. great in importance, extent, or size: it's been a monumental effort. ∎  (of a work of art) great in ambition and scope: the ballet came across as one of MacMillan's most monumental works. ∎  of or serving as a monument: additional details are found in monumental inscriptions.DERIVATIVES: mon·u·men·tal·ism n.mon·u·men·tal·i·ty / ˌmänyəˌmenˈtalətē/ n.mon·u·men·tal·ly / -ˈmentl-ē/ adv.

monumental.
1. Building intended as a monument, or looking like one.

2. Building that is formal, impressive, very large, and permanent, probably intended to overawe.