Colinton Castle was built in the 16th century as an L-plan tower house at least three storeys tall, and was home to the Foulis family. It was added to in the 17th century. In 1650 it was occupied by Cromwell’s troops and was burned by them.
Already in ruins, in the late 18th century the painter Alexander Nasmyth ordered the castle to be partly demolished further to create a more picturesque ruin.
In 2003 the south tower collapsed, and a programme of removal and recording of masonry was carried out.
Colinton Castle stands within the grounds of Merchiston Castle School. The school takes its name from Merchiston Castle where it was founded.