GameCraft Miniatures shows how big some buildings can be, even in 15mm, with the release of their new WWII Government Buildings over in their webshop.
From the release:
GameCraft Miniatures have released a new 15mm building that is perfect for Flames of War and other 15mm WWII wargames. This building features a removable top floor and optional floor and stairs kit for those that want to play inside as well as outside the building. The model measures 15″ x 6.75″ x 6.7″ tall (381mm x 171.5mm x 170mm) and it’s design was inspired by the Reichstag building in Berlin. This is not a true scale representation of the Reichstag (that would be just over 3.5 times this large) but I think you’ll see a family resemblance and agree that this kit is a reasonable size for gaming.