The Lake was created around an old gravel pit in the cornfield which became the Botanic Garden in 1846. The roughly U-shaped Lake was dug out and the soil mounded up in the centre to form a peninsula, which now protects the Bog Garden. This gives some much-needed topography to the Garden. Even the modest four metre high peninsula allows us new perspectives to appreciate the beautiful Lake, the Rock Gardens, the Woodland Garden and the Main Walk.
The Lake covers about one third of a hectare (three quarters of an acre). It has been made watertight with a puddled clay lining, like Hobson’s Conduit and the Stream. The Lake provides an opportunity to grow many different water plants. The western arm of the Lake is partly enclosed by the Woodland Garden and has an intimate feel. There is dense vegetation emerging from the surface - rushes, sedges and sweet flag – with a little open water at the north end. This habitat provides breeding cover for mallards and moorhens, as well as insects such as dragonflies (Odonata).

This part of the Lake also has two trees of the swamp cypress, Taxodium distichum, growing in the water. This species lives in oxygen-poor swamps of south-eastern United States and Mexico. In order to oxygenate the roots, trees send up pneumatophores, or ‘breathing roots’, above the surface of the water. The tree at the southern end of this arm of the Lake has developed an impressive group of pneumatophores, which are often referred to as ‘knees’.

The eastern arm of the Lake has a very different character. The vegetation is dominated by the waterlilies, through which arise the delicate stems and whorled leaves of Mare’s Tail (Hippuris vulgaris), but the overall feel is of an open, sunny lake with mallards and moorhens. The Lake holds a wealth of rudd and other fish which attracts herons and kingfishers early and late in the day.

The Lake provides a wonderful, reflective surface for many spectacular trees. On the eastern side of the peninsula, Acer pseudoplatanus ‘Brilliantissimum’ is a rhubarb and custard-coloured cloud in May, while the Smokebush, Cotinus coggygria, adds ember colours in the autumn. By the lakeshore in the Woodland Garden, reflections of the foxglove-like flowers of Paulownia coreana stipple the still May water with dabs of pale heliotrope. Near the stepping stones the fiery autumn leaves of Liquidambar styraciflua ‘Lane Roberts’ are the most brilliantly-glowing of all trees in this part of the world.