The Tarn is a 9 acres (3.6 ha) site on Court Road between Mottingham and Eltham, in the Royal Borough of Greenwich, southeast London, United Kingdom, consisting of a public garden, a bird sanctuary nature reserve and a lake amongst woodland.

As a garden The Tarn opened in 1935, after the Metropolitan Borough of Woolwich acquired the site from the adjacent Royal Blackheath Golf Course.

The Tarn remains largely unchanged since the 1930s and contains several shelters, benches, a public toilets building and a circular path which crosses a wooden footbridge spanning the lake.

The Tarn, is a site between Mottingham, and Eltham in the Royal Borough of Greenwich, containing a public park, or garden a bird sanctuary, and a lake,[1][2] the vast majority of which is covered in woodland.

[5] An 18th century brick ice house is located in the gardens,[1][6] next to the steps near the northwest bank of the lake,[7] encircled by a small metal fence.

[8][6] The ice house is a Grade II listed structure,[6] and a section of the top has been cut out, but fenced over so people can safely see inside.

[2][3] Opposite the park is a timber yard, and south of the park gates there is parade of shops on the west side of Court Road, including a convenient store, café, hairdressers, off-licence and dry cleaners, there is also a pub named The Royal and a Shell petrol station on the east side of the crossroads to the south.

[3] The northern wooden fence of the bird sanctuary separates the area from the flats of a residential road named Tarnwood Park and the eastern edge of The Tarn is bordered by the grounds of Royal Blackheath Golf Course and Eltham Lodge.

[23] In the mid 17th century the lake had come to be known as Starbuck's Pond,[10][9] at this time Edward Sackville, 4th Earl of Dorset was in charge of the land until the English Civil War when Charles I was captured in 1648,[23] and Rich the rebel with commonwealth soldiers and common people sacked Eltham Palace, destroyed the parks and killed the deer, ending their use as deer parks.

A brick ice house was constructed in the 1750s, on the northwest side of The Tarn lake,[7] it was used by the staff of Eltham Palace,[1] which is around 650 m (710 yd) to the north-northwest.

The Metropolitan Borough of Woolwich constructed a wooden bridge with stone foundations across the lake's narrowest part and landscaped the woodland, then opened the area as a garden and bird sanctuary in 1935.

The wooden bridge across the lake was rebuilt in 1987, using the same stone foundations, and was opened by Mrs Ann Stroud on 24 April that year, with a plaque marking the occasion.

[34][11] In 2009 a pump was installed in the lake to improve oxygen levels, as were a number of small booms, to catch pollution and litter in the water.

[11] In early 2020, Greenwich Council, in response to the COVID-19 pandemic, decided to leave many of its parks, including The Tarn, unlocked and open to the public 24 hours a day, but had to reverse this decision in June the same year, and lock them again at dusk because of concerns of vandalism and other antisocial behaviour.

The architect, Jonathan Bailey, and the planning agent, Peter Turner stated the construction is necessary, to “deliver housing in this country on a national and local level” and this development would provide homes close to public transport.

Adding the construction would “respect the local character and amenity of neighbours” and it would cause “minimum disruption” to residents and visitors of the Tarn.