Complex sentence: The city extended from north to south, from the north border of Tlatelolco to the swamps, which by that time were gradually disappearing to the west; the city ended more or less at the present location of Avenida Bucareli.
Split into simpler sentences: The city extended from north to south, from the north border of Tlatelolco to the swamps. This city ended more or less at the present location of Avenida Bucareli.