Boyce Gulley built the Mystery Castle for his daughter with native rock and anything he could find from the surrounding countryside.

As a child, Mary Lou Gulley loved to build sandcastles and often, Mary's parents, Boyce and Frances would take the young girl to Alki Beach in Seattle. But when the waves came in and washed her castles away, Mary Lou would cry. Her father would comfort her, telling her she was his princess and one day, he would build her a castle big enough to live in. Then, in 1927, four years after Mary Lou was born, her father abruptly left, never saying where he was going or if he would ever return.

Even though he had left them, Mary Lou began receiving letters a few years later, postmarked from Arizona, written by her father. But it was one letter in particular which caused a sting far deeper than ever could be imagine.

“He said he wanted to pursue his dream of being an artist,” Mary Lou once recalled. “It broke my heart that he left us.”

Though the letters came and went as the years passed, he never sent for his family, despite Mary Lou's hope that he'd someday return. For a span of 18 years his whereabouts remained unknown until 1945, when Mary Lou received a telegram from a lawyer in Arizona that informed her that her father had just passed away.

Then came the letter beyond the grave – a final note written by Mary Lou's father and addressed to her, which read:

Dearest Mary Lou:

Can you forgive me?
It wasn't art I wanted, it was you.
I left home not because I wanted freedom but because I had tuberculosis.

So was his confession. Boyce had discovered he had been diagnosed with the much-dreaded tuberculosis in 1929, with only six months to live. To avoid being quarantined in a tuberculosis clinic, and further exposing his wife and three-year-old daughter to the contagious disease, he moved to Arizona in hope that the arid climate would ease his suffering.

While the letter had shed light on his departure, it further revealed a new mystery for the mother and daughter.

After arriving in Phoenix in 1930, Boyce purchased an 80-acre gold mining claim in the desert just outside the city and located adjacent to the town dump. It wasn't long before Mary Lou and her mother set out to Phoenix to see the property the patriarch of the family had secretly owned.

It was 10 p.m. when they arrived in Phoenix, and after checking into a downtown hotel, they decided they couldn't wait for morning to see the property. So on that moonlit night in 1945, mother and daughter took a taxi to the base of South Mountain, knowing only that a house lay near there. But as the taxi neared the property, amid the rock and crevices, rose a five-story castle – the manifestation of a promise made reality.

For the last 15 years, Boyce had toiled away in the desert. With two years of architectural engineering under his belt from a college in Texas, plus an artistic and creative talent, he spent his days collecting natural stone and river rock to form the walls that would make up the castle. As an inveterate recycler, he incorporated old railroad ties, unused telegraph poles and discarded metal into his design.

Before his death, the modern-day 8,000-square foot castle with twisting hallways was completed with 18 rooms, including a caretaker's quarters, a bar, a chapel, 13 fireplaces and a wishing well.

Immediately, mother and daughter moved into the property. But there were stipulations outlined in Boyce's will. The castle was theirs to keep, but on the condition that they followed one peculiar request. Located in the basement, between the chapel and the dungeon, Boyce had built a room known as Purgatory with a trapdoor in the floor. Whatever lay beneath that door was to remain a mystery as Boyce's will stipulated that Mary Lou not open it until January 1, 1948 – a wish Mary Lou honored.

During that time, Mary Lou explored the castle and soon learned more about the epic undertaking her father had taken to build the castle as she found hidden notes left behind loose stone in the walls. These clandestine memoirs would expand upon the journey her father had taken after learning about his contracting tuberculosis.

With little money for building supplies, Boyce spent his days living in an old railroad car while he plotted the construction of the castle on a 40-acre plot of land. During his days, he would roam the valley with his mule, searching for odds and ends which he could use for the construction – often finding many items in the local dump.

As the days passed, Mary Lou's mother contacted Life magazine and informed the editors about the family's castle, along with the mysterious trapdoor. With a crew sent to interview Mary Lou and document the opening of the trap door, everyone waited anxiously on January 1, 1948.

With the trapdoor opened, Mary Lou descended into a dark, 9-foot pit to discover gold, cash, letters from her father and a photograph of him taken just prior to his death. And then Mary Lou discovered a small piece of paper – a valentine she'd made her father when she was a young girl.

On January 26, 1945, Life published the article with the title: Life Visits a Mystery Castle.

While the name stuck, Mary Lou decided to share the mysteries of the castle by offering tours, and would naturally engage visitors with anecdotes of her father and her home. But if Mary Lou was ever bitter about being abandoned by her father, she never let on to strangers. With a firm belief that her legacy lay within the castle, she grew to feel his presence more as she explored the intricacies of the home her father built for her.

Over the next 65 years, Mary Lou would share many stories with guests, granting tours until her death on November 3, 2010. In her obituary, she is identified as the “resident princess and proprietress of Mystery Castle.”

To date, tours are still held at Mystery Castle Thursday through Sunday from October to June for $10 for adults and $5 for children ages 5-15.