Largest lake in Great Britain measured by surface area.

Scattered throughout London are ancient remnants of the city's former bounding wall.

Hear the quietest sound from across the dome.

An unusual round church in London with a Templar past.

Four cars from the old system were once on display, but were removed in 2014.

A massive forgotten storehouse from 1913 on the Brooklyn Waterfront has a spectacular view of Brooklyn.

Ride the subways of yesteryear.

An artist's cute bronze subway sculptures belie his violent artistic past.

The most confusing clock in New York.

This sculpture by artist Fritz Keonig survived the 9/11 attacks and now stands as a monument to the victims.

Blighted Irish field and the ruins of a 19th-century cottage on the edge of urban Manhattan.

Unrepaired walls from a 1920 anarchist bomb attack.

Manhattan's lighthouse, erected at the insistence of the unsinkable Molly Brown.

A pyramid in Central Europe of unknown origin.

Site of the 1889 murder-suicide of crown prince Rudolf and his lover Mary Vetsera.

Giant WWII fortresses that fired 8,000 rounds a minute, now home to thousands of pigeons.

One of the best collections of wax anatomical models in the world.

Macabre museum devoted to historical Viennese murders.

Annual technopop celebration of peace and love.

A small museum filled with over 1,000 clocks, and one particular clock calibrated to run until the year 9999.

The final resting place for the remains of 143 Habsburg royalty.

Baroque celebration of the end of the Great Plague of Vienna.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

The Pope’s secret escape route.