The city of Moscow has gradually expanded in a series of concentric rings around the Kremlin. The result is four defined rings divided into sections by the wide avenues branching out from the centre. Beyond the Kremlin, the second circle is made up of the old district of Kitai Gorod, which was once encircled by fortifications but today only has a few remains. The third ring, the Boulevard Ring, used to be the outer boundary of the 'White City'. The last ring, known as the Garden Ring, marks the border between the city and its modern suburbs. The Moscow Ring Road delineates the outer limit of the city .