Much of Mesoamerica's rich cultural heritage is slowly eroding because of acid rain. Just as water dissolves an Alka-Seltzer tablet, acid rain erodes the limestone surfaces of Mexican archaeological sites at a rate of about one-half millimeter per century (Bravo et al. 2003). A half-millimeter may not seem like much, but at this pace, a few centuries of acid rain is sufficient to destroy paintings, frescoes, and other fine detail in ancient art and architecture. This article describes an interdisciplinary educational supplement designed for middle-and high-school classrooms called "Acid Thunder: Saving El Tajin from Acid Rain." This supplement came about as a result of research conducted by the University of Wisconsin-Milwaukee in collaboration with the National Autonomous University of New Mexico (UNAM). The supplement is in the form of a Webquest, an inquiry-oriented exercise focusing on analysis, synthesis, and evaluation, for which the Internet is the primary information source. "Acid Thunder" is two-week activity that follows the work of a group of UNAM scientists who are researching many aspects of acid rain, including chemistry; meteorology; effects on plants, animals and materials; and measurement. "Acid Thunder focuses on the El Tajin archaeological zone, an important monument site in the state of Veracruz, Mexico. The Webquest is designed as an interdisciplinary unit to facilitate standards-based, active exploration in science and social studies. With "Acid Thunder", teachers have the significant opportunities to integrate topics in science and social studies and can offer students a stimulating experience likewise students can research features of an ancient Mesoamerican culture and compare it with other pre-Hispanic civilizations like the Mayas or Aztecs. In addition, this Webquest serves the important function of demonstrating to students how classroom walls are no longer a boundary for classroom-based activities. (Contains 2 figures.)