Ancient catacombs form the foundation for this Rococo orgy of a church.

This Gallo-Roman sanctuary is dedicated to Serápis, god of the underworld.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

This oddly shaped church resembles a rocket.

One of the smallest bookstores on the planet.

Hidden beneath a beautiful overlook you’ll find the history of the city depicted in comic strip format next to a pay toilet.

Ring the bell to enter a bar that looks equal parts museum and old curiosity shop.

Tucked away inside this concrete building is a church and its grand display of brutalist architecture.

A discarded movie prop that was the original monolith for "2001: A Space Odyssey."

The barrel-made lookout from Shackleton's final ship is tucked away in the crypt of one of London's oldest churches.

The 2,000-year-old beam is tucked within the pedestrian entrance to the old London Bridge.

The commemorative stone column conceals a secret laboratory.

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

London's amazing modernist public square that never was.

A secluded green oasis amidst the towering skyscrapers, bears an unusual moniker that reflects one of the city's oldest guilds.

What might be the oldest living tree in London has survived fires, bombings, and estate agents.

A mysterious carving from 17th-century London seemingly depicts a young boy sitting on a bread basket.

The ruins of a church destroyed by both the Great Fire of London and the Blitz, now turned into a peaceful garden.

A quiet memorial to those who died saving others in the heart of the City of London.

It's a mystery why these remains were found with no traces of their bodies in sight.

A tribute to all the green-thumbed workers who tend London’s public parks and gardens.

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

Originally built for London’s cab drivers, this bright green hut now serves anyone a hot drink or meal.

The Art Deco artwork depicts gilded carriers of deadly illnesses.