Edinburgh Castle is one of the most popular visitor attractions in the UK and the most popular ticketed attraction outside of London. It gets approximately two million visitors per year.
It has 27 individual buildings spread over 7 acres, including an active military base.
Its size and large number of visitors makes the castle the largest consumer of energy managed by Historic Environment Scotland, the public body tasked with investigating, caring for and promoting Scotland's historic environment.
Despite the increasing numbers of tourists, it has been able to reduce energy consumption by 29% and carbon emissions by 31% since 2008.
This remarkable decrease has been achieved by using more energy efficient lighting, adding insulation and replacing gas boilers, controls and pumps, among other improvements.