The Mausoleum of Halicarnassus was one of the seven wonders of the ancient world. It is now in the British Museum in London and groups in Turkey  have for some time campaigned for its return.
You can add your signature to their petition here .
Hurriyet Daily News 
Campaign started for relic
ISTANBUL – Hürriyet Daily News
A digital signature campaign has been initiated ahead of a lawsuit that will be opened at the European Court of Human Rights (ECHR) in January for the return to Turkey of the Halicarnassus Mausoleum.
According to a written statement, several artists have signed the campaign on the website www.askinmabedi.com. The signatures will be collected as part of the lawsuit lawyer Remzi Kazmaz will file, with 30 other lawyers, at the ECHR on Jan. 30.
A documentary film about the event will also be included in the lawsuit. Directed by Kazmaz, the 32-minute film “Aşkın Mabedi-Maussolleion” is the story of the ancient treasure being taken out of Turkey.
The film, which also has an English version, will be viewed by ECHR officials as well as sold in music stores across Turkey. The mausoleum is one of the Seven Wonders of the World and is currently located at the British Museum.