Thermal springs underneath the seabed provide the heat and bubbles for these beachside natural hot tubs.

This mountaintop lake bubbles and steams in a perpetual boil, thanks to its direct link to the Earth's interior.

This stone commemorates the island's launch into international aviation.

This popular tourist cave was ignored for almost 200 years before being mined into an attraction.

Tiki luxury on Nob Hill.

San Francisco's oldest surviving monument and meeting place for 1906 survivors.

The oldest house in the capital of Silicon Valley.

It took years to decode its mysterious messages.

This restaurant's marvelous musical machines include a self-playing violin.

The headquarters of the semiconductor giant has a 10,000-square-foot museum.

A memorial to the only dog ever officially enlisted in the Royal Navy.

Formerly known as the Malay Quarter, Bo Kaap is a colorfully-painted suburb located in the “Mother City” of South Africa.

A sobering account of the vibrant multicultural neighborhood that was destroyed under apartheid.

Despite many attempts to finish this overpass, it has been abandoned since the 1970s.

One of the few standing Roman lighthouses and a labyrinth of tunnels are a couple of the secrets at this historic castle.

The dance of this huge clock is a magnificent and eerie commentary on good and evil in the history of humankind.

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

A verdant 17th-century-style garden hidden along Edinburgh’s Royal Mile.

The largest terracotta fountain in the world, built to commemorate Britain’s Victorian achievements.

One of the first monuments dedicated to the accomplishments of the great Vice Admiral, Horatio Nelson.

The old tradition of drying laundry on poles in the public green is still guaranteed by Glasgow city law.

An icon of the Battle of Britain is frozen in flight in a grand Victorian museum.

This stately monument has been wearing a traffic cone hat for decades much to the delight of the locals.

Since 2017, the remains of Stretford's industrial past have been occupied by a collection of gnomes.