Spear Tower

The Spear Tower is the dominant structure in Sunspear, the seat of House Martell. It is a 150-foot structure with a pinnacle of shining steel

In the books
In the A Song of Ice and Fire novels, the Spear Tower is a massive tower of stone, thrusts up from the surrounding community, stretching one hundred and fifty feet tall, with a spear of gilded steel atop that adds a further thirty feet. Highborn prisoners might be confined in cells at the top of the Spear Tower.