Boettcher Memorial Tropical Conservatory

Denver Botanic Gardens, founded in 1951, moved in the late 1950s to York Street in the Cheesman Park neighbourhood, on the site of the former Prospect Hill cemetery. In 1958 Ruth and James Waring donated a 1926 mansion to serve as headquarters, and the grounds began to be laid out under the direction of the San Francisco landscape architect Garrett Eckbo.

The great tropical conservatory was designed in 1964 by two Denver architects, Victor Hornbein and Edward D. White Jr. It bears the name of the Boettcher family, whose foundation, established by Claude K. Boettcher and his son Charles, paid for it. Dedicated in 1966, it is described as the first conservatory in America built entirely of concrete and Plexiglas. In 1981 Hornbein added a Bromeliad House at its west end for flowering tropical plants.

In 1973, barely seven years after it opened, the building was designated a Denver Landmark, an unusually early recognition for such recent architecture.

The conservatory breaks with the Victorian formula of a glazed metal frame. Its structure consists of interlaced, cast-in-place concrete arches rising about fifty feet (roughly 15 m) above the tree canopy, with faceted Plexiglas panels filling the spaces between them to create a crystalline shell. Each pane was designed to channel condensation to the sides so that it would not drip onto visitors.

Inside, a sloping, naturalistic landscape holds waterfalls and pools. The architects paid close attention to finishes: flagstone paving and trim, oak doors set in steel frames, and geometric leaded stained glass. A fabricated two-storey banyan tree, placed midway along the circular path, lets visitors view the indoor forest at several levels. The planted area covers more than 11,000 square feet, or about 1,000 m².

The conservatory displays plants from tropical and subtropical regions, around 600 species according to the Colorado Encyclopedia, in a warm and humid atmosphere. Large tropical trees form the upper storey, which the artificial banyan brings within close view. Orchids and bromeliads are shown in rotating displays in another of the garden's spaces, Marnie's Pavilion. The full plant inventory can be searched in the garden's online Gardens Navigator.

The conservatory is part of Denver Botanic Gardens' main York Street site, within its sequence of internationally inspired gardens. The circular path and the climb into the banyan take about half an hour. In cold weather it offers a striking contrast with the outdoor gardens, which include what is described as North America's largest collection of plants from cold temperate climates, a Japanese garden opened in 1979, the Bill Hosokawa Bonsai Pavilion (2012) and the Science Pyramid.