Built "to last 1000 years," the Great Stupa at the Shambhala Mountain Center near Ft. Collins in the Colorado Rockies was built with the finest, most durable materials available. Silica fume, fly ash, a high-range water reducer, and a retarder were added to the high-performance concrete used in the 100-foot-tall structure. Impermeability was achieved by a combination of low water-cement ratio and pozzolanic additives that reduced voids in the concrete. A combination of superplasticizer and retarder created a highly workable concrete.