This coffee shop lies hidden beneath a historic church.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

A mysterious pair of mice eating a piece of cheese is London's smallest public sculpture.

The Great Fire of London and the regulation of one-way streets both started in this alley.

The commemorative stone column conceals a secret laboratory.

The taxidermied remains of a once-great parrot.

Dictionary Johnson’s favorite feline.

A hands-off space for graffiti artists to hone and display their skills.

A naturally mummified 2,000-year-old man.

An easily overlooked stretch of ornate window fronts and gaslight lamps that could be right from the pages of Dickens.

A charming 17th-century alley is lined with secondhand bookstores and antiquarian shops.

This hidden green space is the city's second largest conservatory.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

This former Roman Catholic Church still contains the embalmed hearts and organs of 22 popes.

Architectural monsters are devouring this palace's every door and window.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

Charles Dickens was not a fan of the ghastly wall dressings in this 6th century church.

A huge enchanting public park just outside the ancient walls of Rome.

This hydrochronometer was invented by a Dominican monk and is a prime feature in this garden.

Don't get it twisted: This is the oldest pretzel bakery in the United States.

Once part of a dam servicing an early 19th century grist mill, the tucked-way falls are a tricky-to-find urban oasis.

A swimming hole in the historic industrial quarry that supplied the marble for the Baltimore Washington Monument.

Yo, Adrian!

The world’s first penitentiary, meant to be humane, drove men insane.