Boghall stands near the town of Biggar in South Lanarkshire.
It was a strong castle, situated in a marsh and approached by a bridge over a moat then through a gatehouse. A tower house occupied the centre of the courtyard. The curtain walls were defended by vaulted, D-shaped, gun towers.
In 1670 the tower house was demolished and replaced by a modern mansion. By the end of the 18th century the castle was in ruin but substantially intact. The 19th century saw it robbed out for its stones until the only remains visible were the stair tower of the mansion and the 2 towers of the curtain.
In 1870 one of these (that pictured) collapsed prompting a cry to preserve what was left.
An interesting aside on its strength is provided by an event in 1651 when its Cromwellian garrison felt secure enough to refuse the summons to surrender by Charles II when his army stopped at Biggar on its march to the south.