Work has begun on a £4m project to construct a visual arts space at City Observatory on Calton Hill in Edinburgh.

Artistic group Collective aims to preserve the building's William Henry Playfair designs while creating an underground gallery.

The project, which also includes a restaurant, is due for completion by the end of next year.

It is hoped the new venue, which will exhibit the work of national and international artists, will become a landmark destination for visitors.

The observatory's original 19th century features will be retained alongside its telescopes, astronomical instruments and the surrounding grounds.

The start of the work on Wednesday marked a milestone for the conservation of the observatory, which is on the Buildings at Risk Register.

Collective's project has been funded by various trusts and foundations, the Heritage Lottery Fund, Edinburgh City Council, Creative Scotland and Edinburgh World Heritage.

Kate Gray, director of Collective, said: "We are thrilled to be at this point in the project and are now able to see our vision becoming a reality.

"This innovative project is the culmination of five years of work and would not be possible without the huge amount of support from artists, individuals and funders we have received.

"We are very excited to see our plans progress over the next year and we look forward to welcoming people to a new kind of City Observatory when we open the site freely to the public for the first time in its history."