I recall very much enjoying horror movies which had castles and mansions riddled with secret rooms and hidden passages. I still enjoy these in a story. I can recall seeking secret rooms in our house when I was a child, absolutely convinced that there had to be some mysterious places in our ordinary abode.
Crossing magical boundaries is also a favorite theme. Several of my little stories have this theme as an element. I recall several writers who used these mystical transitions, Lovecraft chief among them. I think the prospect was particularly sweet to my young mind, so many years ago. It promised escape from the mundane, high adventure, infinite possibilities.
Powers of magic were also appealing. The prospect of the "little guy" being able to obtain powers to right wrongs and protect the innocent seemed very appealing to me. Even today this appeals to me. In the game World of Warcraft my primary character is but two feet tall, yet a very powerful fire mage.
Perhaps it is the power to overcome obstacles which I found appealing. The power of secret places, allowing resources to be accumulated and created under the eyes of the enemy. The power to move in unconventional ways, circumventing the counter moves of opponents. The power to simply overwhelm enemies with power itself.
Quite appealing to a "little guy" who might be overwhelmed by a big world. Mysterious powers, unknown and unanticipated by worldly opponents. I am not so little, now. Still, the world is greater, and often overwhelming. I might just like to withdraw to my secret lair, beyond a mysterious barrier, where I can learn to master unbelievable powers to overcome all who oppose me.
Yes, quite appealing, indeed.