Settled in turn by Native Americans, Spaniards, Mexicans and Yankees, NEW MEXICO is among the most ethnically and culturally diverse of all the states in the US. Each successive group has built upon the legacy of its predecessors; their various histories and achievements are closely intertwined, and in some ways the late-coming white Americans from the north and east have had comparatively little impact. Signs of the region's rich heritage are everywhere, from ancient pictographs and cliff dwellings to the design of the state's license plates, taken from a Zia Indian symbol for the sun - the one near-constant fact of life in this arid land. <br> New Mexico's indigenous peoples - especially the Pueblo Indians , as the name suggests clear descendants of the Ancestral Puebloans - provide a sense of cultural continuity. Despite the Pueblo Revolt of 1680, which forced a temporary Spanish withdrawal into Mexico, the missionary endeavor here was in general less brutal than elsewhere. The proselytizing padres eventually co-opted the natives without destroying their traditional ways of life, as local deities and celebrations were incorporated into Catholic practice. Somewhat bizarrely to outsiders, grand churches still stand at the center of many Pueblo settlements, often adjacent to the underground ceremonial chambers known as kivas , and almost always built in the local adobe style. <br> The Americans who took over from the Mexicans in 1848 saw New Mexico as a useless wasteland. But for a few mining booms and range wars - such as the Lincoln County War, which brought Billy the Kid to fame - New Mexico was left relatively undisturbed until it finally became a state in 1912. During World War II, it was the base of operations for the top-secret Manhattan Project , which built and detonated the first atomic bomb, and since then it has been home to America's premier weapons research outposts. By and large, people here work close to the land - mining, farming and ranching - with tourism increasingly underpinning the economy. Northern New Mexico centers on the magnificent landscapes of the Rio Grande Valley , which contains its two finest cities: Santa Fe , the adobe-fronted capital, and the artists' colony and winter resort of Taos , with its nearby pueblo. More than a dozen Pueblo villages can be found in the mountainous area between the two, while to the west lie the evocative ancient ruins at Bandelier and Puyé . The broad swath of central New Mexico along I-40 - the interstate highway that succeeded the old Route 66 - pivots around the state's biggest city, Albuquerque , with the extraordinary mesa-top Pueblo village of Ácoma ("Sky City") an hour's drive to the west. In wild and wide-open southern New Mexico , the deep Carlsbad Caverns are the main attraction, while you can still stumble upon old mining and cattle-ranching towns that have somehow hung on since the end of the Wild West. <br> For many visitors, the defining feature of New Mexico is its adobe architecture , as seen on homes, churches, and even shopping malls and motels. Adobe bricks are a sun-baked mixture of earth, sand, charcoal and chopped grass or straw, set with a mortar of much the same composition, and then plastered over with mud and straw. The color of the soil used dictates the color of the final building, and thus subtle variations can be seen all across the state. However, adobe is a far from convenient material: it needs replastering every few years and turns to mud when water seeps up from the ground, so that many buildings have to be sporadically raised and bolstered by the insertion of rocks at their base. These days, most of what looks like adobe is actually painted cement or concrete, but even this looks attractive enough in its own semi-kitsch way, and hunting out such superb old adobes as the remote Santuario de Chimayó on the " High Road " between Taos and Santa Fe, the formidable church of San Francisco de Asis in Ranchos de Taos, or the multitiered dwellings of Taos Pueblo , can provide the focus of an enjoyable New Mexico tour. <br> You'll also become familiar with another New Mexico trademark, the bright-red ristras , or strings of dried chili peppers , that adorn doorways throughout the state; festooned on restaurant entrances, they serve as warnings of the fiery delights that await within.