The central Mexican city of Xochicalco was established around a.d. 670 atop a 400-foot-tall hill. At the city’s highest level, which was only accessible through three defended porticoes, stands its ...

Trusted, comprehensive information and resources for heart health. Chest pain isn’t always a heart attack, but it’s safer not to guess. Know when symptoms mean it’s time to get help. It's not just ...

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