Which famous Chicago structure is known for its series of arches and is a major skyline feature?

The John Hancock Center stands out as a prominent feature in the Chicago skyline, particularly due to its unique design that includes a series of distinctive structural elements. One of the most notable aspects of the building is its use of a braced system of steel that creates a series of angles and lines that visually resemble arches, contributing both to its aesthetic appeal and its structural integrity.

Moreover, the combination of its height and architectural design makes the John Hancock Center not only a key skyline feature but also an iconic symbol of Chicago. Its observation deck and angled roof, along with the distinctive black façade, further emphasize its significance in the city’s architectural landscape.

In contrast, the other options, while notable in their own right, do not possess the same characteristic of arches or prominent skyline presence associated with the John Hancock Center. The Willis Tower, for example, is known for its tiered design, the Tribune Tower features a neo-Gothic style with ornate detailing, and the Chicago Water Tower is recognized for its historic significance and limestone structure. Each of these buildings contributes to the architectural diversity of Chicago but does not embody the specific qualities mentioned in the question.