In a broad sense, Tojo refers to city at large surrounded by walls (walled city) and, in a more limited sense, it refers to a capital or secondary capital city (Baito) designed and constructed in conformity with 'jobosei' (street plan of ancient capital) whose city area was surrounded by walls called 'Rajo'.
都城とは広義には城壁で囲まれた都市全般を指すが（→城郭都市）、狭義には「条坊制」に則って設計・建設された首都あるいは副都（陪都）で、「羅城」と呼ばれる城壁で市域を囲郭されたものをいう。