The east face of the Castillo (Structure A-6), the largest structure at Xunantunich, as it appeared in 1991. A restored stucco frieze can be seen at the top. Photo: Guillermo Aldana.

A view from 1993 of the Castillo's west face, as seen from its base. The 130-foot pyramid dominates the site. Photo: Guillermo Aldana.

Excavation of the west frieze of the Castillo in 1997 by the Xunantunich Archaeological Project (XAP) team. Photo: J. Scarborough, © Xunantunich Archeological Project, The Cotsen Institute of Archaeology at UCLA.

Haydee Orea of the Instituto Nacional de Antropología e Historia in Mexico undertakes conservation of the newly excavated west frieze of the Castillo. Following excavation, study, and conservation, the west frieze was reburied to protect it for the future and a replica made for public viewing. Photo: Guillermo Aldana.

A close-up of fungal growth on a wall of the Castillo. Photo: Valerie Dorge.

The autonomous environmental monitoring station, designed by GCI staff, at the Xunantunich site. Data from the station was used to define conditions for artificial aging tests in the laboratory and to evaluate the testing in the field. Photo: J. Scarborough, © Xunantunich Archeological Project, The Cotsen Institute of Archaeology at UCLA.

Angie Hiltz of XAP sketches the west face of the Castillo, as part of documentation in 1993. Structure A-1 is visible in the background. Photo: Guillermo Aldana.

Excavation in 1993 of the west side of the Castillo, which revealed eroded core material and large structural cracks. The conservation team worked to develop methods to stabilize structures such as this with as little change to the original appearance or construction as possible. Photo: Guillermo Aldana.

The south face of Structure A-1 in 1993, with new core facing being installed. Following the excavation of fallen debris, eroding terrace walls are stabilized by the addition of a new skin of rubble core material. Photo: Guillermo Aldana.

Two photographs of the north face of Structure A-1, the top taken in 1993, the bottom in 1995. The images show the progress of conservation over time, capturing the transformation of unexcavated mounds into consolidated structures. Photos: D. DeVries (1993), T. Torres (1995), © Xunantunich Archeological Project, The Cotsen Institute of Archaeology at UCLA.