To truly understand this palace, you must look down as well as up. Beneath the current stone floors lie the ruins of two former castles, including the original fortress built by Bishop Absalon, the founder of Copenhagen, in the year 1167. When workers were digging the foundations for the modern palace in 1907, they accidentally struck ancient limestone walls. Today, you can visit these subterranean excavations and see the remains of the infamous Blue Tower, a medieval prison where Leonora Christine, the daughter of King Christian the Fourth, was held captive for nearly 22 years. The palace you see today is actually the third Christiansborg to stand here, after devastating fires in 1794 and 1884 reduced its predecessors to smoke and ash. It is a masterpiece of resilience, reborn in 1928 in a grand style meant to symbolize the nation's strength.