Greencastle is a small village located on the southern shore of Carlingford Lough, in County Down, Northern Ireland. The village is situated at the foot of the Mourne Mountains, and it is known for its beautiful scenery and historic castle.

The castle, which dates back to the 13th century, was built by Hugh de Lacy, the first Earl of Ulster, as a stronghold to defend the region against attacks from the Irish clans. Today, the castle is a popular tourist attraction, and visitors can explore its ruins and learn about its rich history.

In addition to the castle, Greencastle is also a popular spot for outdoor activities, such as hiking, fishing, and boating. The village has a small marina where visitors can launch their boats and explore the scenic Carlingford Lough. The lough is also home to a variety of marine wildlife, including seals, dolphins, and porpoises.

Overall, Greencastle is a charming village with a rich history and stunning natural beauty. It is a popular destination for tourists looking to explore the scenic Carlingford Lough and the surrounding region.