The Garden of Cosmic Speculation is at Portrack House, near Dumfries in South West Scotland. It is a private garden created by Charles Jencks. The garden is inspired by science and mathematics, with sculptures and landscaping on these themes, such as Black Holes and Fractals. The garden is not abundant with plants, but sets mathematical formulae and scientific phenomenae in a setting which elegantly combines natural features and artificial symmetry and curves. It is probably unique among gardens, drawing comparisons with a similarly abstract garden in Scotland, Little Sparta.
The garden is private but usually opens on one day each year through Scotland's Gardens Scheme and raises money for Maggie's Centres, a cancer care charity named for Maggie Keswick Jencks, the late wife of Charles Jencks.
The garden is the subject of an orchestral composition by American composer, Michael Gandolfi, which he composed for a joint commission from the Boston Symphony Orchestra and the Tanglewood Music Center. The piece was subsequently recorded by the Atlanta Symphony Orchestra conducted by Robert Spano, and nominated for "Best Contemporary Classical Composition" at the 2009 Grammy Awards.