Greece
Not much remains of this once-massive temple to Zeus, though the standing columns can still give you a sense of the temple's scope.
Greece
The Acropolis of Athens is perhaps the essential centerpiece of Western civilization. It features the Parthenon, the remarkable Erechtheion, and the temple of Athena Nike.
Germany
This museum has an impressive array of Roman artifacts that were found along the Rhine. Cologne, while now thoroughly modern, was initially a major Roman city and many remains have been discovered and are on display here. The museum is also built on the ruins of a significant Roman villa with a large Dionysus mosaic on display.
Peru
Machu Picchu is one of the most stunning places in the world. Likely constructed as an estate for the Incan emperor Pachacuti, the city of Machu Picchu was built in the middle of the fifteenth century. Perched improbably on a plateau among sheer mountains, Machu Picchu is astoundingly photogenic, but it's even more impressive in person.
France
This chateaux is more ruins, but is a fun climb through. The very small fee grants you a card to read in a variety of languages that leads you through this castle that has been standing since the 12th century.
Estonia | France
More ruins than anything else, the castle offers rampart walks, beautiful views of the harbor below, and some local art exhibits.
Italy | Sicily
The ruins of an ancient Greek city on a picturesque ridge in central Sicily, Morgantina is an active archaeological site. That means it's well-preserved, but visitors unfortunately can't walk through the main town area with the agora, theater, market, and some of the larger houses. However, you can see the ruins from a hill that gives you a very good overview of this ancient town, and it's possible to walk through some of the outlying homes.
Italy | Sicily
This Roman villa is one of the most remarkable, awe inspiring, and unexpected archaeological sites we've ever visited. The building itself is impressive enough, but the real attraction is the 60 mosaic floors that are stunningly well-preserved.
Italy | Sicily
The Greek settlement of Agrigento once boasted a series of impressive temples along its southern wall. Today only four remain, and they exist in varying states of ruin.
France
Lyon was founded as the roman city of Lugdunum in 43 AD and was the Roman capital of Gaul. This well done museum is built on a hill overlooking Lyon (take the funicular to get up here) and includes two impressive roman theaters.