A 16th-century fountain marks the site of a lost medieval cemetery once filled with mass graves.

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

Displaced highlanders would take shelter from the wet Scottish climate under the large walled bridge at Glasgow Central Station.

A scattered trail of street art adds a pop of color to the city's stark structures.

The elaborate clockwork contraptions in this Scottish gallery create small worlds of whimsy and horror.

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

Overlooked by many, the two famous Scottish warriors guard the main gate of Edinburgh Castle.

Accessible only at low tide, the deserted island is dotted with World War II ruins.

Remnants of the 16th-century defensive wall still stand unassumingly within Edinburgh.

The 16th-century church has the only stained glass windows that survived the Scottish Reformation intact.

There are plenty of wonderful panoramic vistas in Edinburgh, but not many are hidden smack in the middle of the Old Town.

The mummified heart of a saint lives on in this church—after a brief hiatus when it was stolen.

This permanent collection of preserved bodies taken from Irish bogs is one of the leading authorities on such morbid mummies.

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

A 2000-year-old Roman amphitheater lies just below Guildhall Yard.

An incarceration museum on the spot of possibly the oldest prison in England.

The last four extravagant street signs of London's historic banking street.

The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

The remains of an ancient Roman teenager are memorialized at the base of a modern London landmark.

A museum wholly devoted to juvenescence.

The remains of the great moral philosopher reside in a university in London.

The site of London's first coffee house has been serving refreshments of one kind or another for 360 years.

Public access to clean drinking water was an instant hit among the masses.

Remnants of cells from the most notorious London prison may lie in the basement of a rare Victorian Gin Palace.