A network of concealed passageways lies within a busy London Underground station.

This magical museum celebrates the life and work of a seminal children's book writer (and occasional spy).

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

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

Hidden in a grotto 26 feet below Nottingham's oldest hotel, this stylish subterranean drinking den is notoriously hard to find.

A historic arboretum and non-conformist, non-denominational park cemetery.

The sixth of London's "Magnificent Seven" cemeteries, and a source of unlikely inspiration to Beatrix Potter.

One of the world's largest collections of pathological specimens.

A collection dedicated to the treatment of disease, held in London's oldest hospital.

The largest greenhouse in the world is home to over one million types of plants.

Surreal riveted sea forts once protected the Kent shores from German attack.

The anatomical-pathological collection of a man who changed surgery.

The world's first underground farm is in a World War II bomb shelter beneath the streets of London.

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

Built to test magnetically levitated elevators, the tower also boasts Germany's highest visitor platform.

This painted Lego bridge is the product of over a century of locomotive history.

This "floating railway" is one of the world's oldest monorail systems.

The fairy tale castle of the "fairy-tale king."

The South African dialect's complex history is immortalized in stone, in one of the world's only monuments dedicated to a language.

Spanning the El Chorro gorge, this pathway used to be one of the most dangerous crossings in the world.

Strolling through these vintage locomotives offers a surprising amount of insight into the history of Kenya.

The designer of this railway tunnel added a birthday present for himself.