A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

The United States Capitol's former columns still stand.

This 2,000-year-old Doric bridge is still open to pedestrian traffic to this day.

The oldest housing complex in Riga is a mini timeline of architectural trends.

This ducal residence was once home to a future Russian empress and a French king in exile.

Over time, this castle grew to encompass the entire island.

The former Nazi concentration camp stands as a museum to remember this dark chapter in European history.

Poland's oldest surviving university building holds a wealth of historic science instruments including some used by Copernicus.

St. Mary's features one of the most spectacularly decorated cathedral interiors in all of Europe.

In this museum, visitors are invited to touch the art.

Legend has it this fountain built to symbolize the Pope’s power hides a strange secret concerning Neptune's manliness.

This is the oldest Roman-made bridge in the city still existing in its original state.

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

Installed in an act of one-upsmanship, the annual sundial in this church is also a symbolic victory for the Gregorian calendar.

Legend has it that any woman who kissed this statue would soon be married.

The roof of this ancient mausoleum is made from a single Istrian stone weighing a massive 230 tons.

A medieval, mosaic-lined baptistry built by a heretical Christian sect.

Psychoanalyst Carl Jung reported a paranormal experience after visiting this mosaic-lined Roman baptistry.

An incredible mosaic-lined monument said to have held the remains of an ancient Roman empress.

This 6th-century church has the largest and best-preserved collection of Byzantine mosaics outside Constantinople.

Italian poet Dante Alighieri is entombed in this small mausoleum in Ravenna, and his hometown of Florence has never been too happy about it.

Filled with goldfish swimming in a shallow pool of sea water, this ancient crypt is more wishing well than burial site.

Stuck in the arcade of Casa Isolani are three arrows of mysterious origins.