<P> In 2005, Monterrey was ranked one of the safest cities in Mexico, and one of the two safest in 2006 . But since 2008 it has experienced violence related to turf battles between warring drug cartels . The year 2011 was the most violent in history . Drug dealers are a major concern, although military offensives and police captures of important drug - cartel chiefs have weakened cartels trying to settle in the city . The city is safe to travel by day and night, but common - sense precautions should be taken in certain districts at night . </P> <P> There are two police departments in the city, the Police of the City of Monterrey (locally known as the Policía Regia), dependent on the municipal government, and the State Public Safety . The Policía Regia protects the city's downtown and main areas, while the State Public Safety is in charge of remoter areas . Since the 2011 attack on the Casino Royale, security has been reinforced by military and federal police . </P> <P> The city of Monterrey is 540 metres (1,770 ft) above sea level in the northeastern state of Nuevo León . Monterrey translated from Spanish to English is "King Mounds", which refers to the city's topography and the large mountains that surround it . The Santa Catarina River--dry most of the year on the surface but with flowing underground water--bisects Monterrey from east to west, separating the city into north and south halves, and drains the city to the San Juan River and Rio Grande . </P> <P> Monterrey is adjacent to San Nicolás de los Garza, García and General Escobedo to the north; Guadalupe, Juárez and Cadereyta Jiménez to the east; Santiago to the south; and San Pedro Garza García and Santa Catarina to the west . Their combined metropolitan population is over 4,080,329 people . </P>

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