Tower Bridge as its northern landfall is in Tower Hamlets. The bridge consists of two bridge towers tied together at the upper level by two horizontal walkways, designed to withstand the horizontal tension forces exerted by the suspended sections of the bridge on the landward sides of the towers. The vertical components of the forces in the suspended sections and the vertical reactions of the two walkways are carried by the two robust towers. The bascule pivots and operating machinery are housed in the base of each tower. Before its restoration in the 2010s, the bridge's colour scheme dated from 1977, when
London Bridge Is Falling Down London Bridge Is Broken down With a gay Lady.</poem> A version from James Ritson's "Gammer Gurton's Garland" (1784) is similar but replaces the last verse with: <poem> Build it up with stone so strong, Dance o'er my Lady lee, Huzza! 'twill last for ages long, With a gay lady.</poem> The meaning of the rhyme is not certain. It may simply relate to the many difficulties experienced in bridging the River Thames, but a number of alternative theories have been put forward. One theory of origin is that the rhyme relates to the supposed destruction of London Bridge by Olaf II