Where Freemasons go, mystery and intrigue follow. The centuries-old fraternal organization is often described as the world’s largest secret society; while its existence has long been acknowledged, only members know what takes place within their magnificent lodges and at their exclusive meetings.

The Masons began as a simple trade guild for builders in the Middle Ages, but over the centuries morphed into a social organization resembling ancient religious orders, with symbolism, elaborate costumes, and strict rules governing the conduct of members. As their ideals and rituals spread around the world, renowned men (and yes, it’s pretty much only men) such as George Washington, Mozart, Voltaire, and Mark Twain became members, but only after a rigorous admission process and being sworn to secrecy.

As a result, many myths have come to surround the order, and while some of these have been clarified, a large part of the masonic ethos remains unknown to outsiders. The curious may find clues lurking in the order’s lavish lodges and temples in cities around the world, some of which were once hidden or inaccessible but now can be visited and explored. Here are 14 such spots where the Freemasons have left their enduring mark.