Tantallon Castle, a badass medieval fortress in Scotland, was built in the mid-14th century by William Douglas, the 1st Earl of Douglas. Perched on a cliff overlooking the Firth of Forth, this castle boasts a single massive wall protecting its promontory location. Despite facing sieges and battles over the centuries, it remained in the hands of the Douglas family until the 17th century. Today, this epic ruin is looked after by Historic Environment Scotland, giving visitors a glimpse into its storied past.