Roman triumphal columns were massive structures erected in the city of Rome to celebrate massive victories in battle against enemies. These arches were huge structures with minute details of the battle's events and signifiers of the people who were defeated. These triumphal arches were used as models for many later arches in European history, such as the Arc de Triomphe in Paris.

Bas-relief a very ancient artistic form. Bas-relief, from the French for "low relief," is a sculpture that leaves a background in the medium, carving only a portion of the front of the image into the stone being used. Bas-relief was first developed by the Ancient Egyptians, and widely used in Classical Greece and Rome.

Both Kouros (c. 600 BCE) and Dying Warrior from the Temple of Aphaia (500-490 BCE) are works of Archaic Greek sculpture. Kritios Boy is from 480 BCE and is an early work of the Classical period. Laocoon and His Sons (c. first century CE) is from the late Hellenistic period.

The Ionic order was named after the region of Ionia, a smattering of islands between Greece and Asia Minor (modern day Turkey), which were settled by Greeks in roughly the seventh century BCE. While the Ionians were there, they adapted Greek architecture into a simpler form, with more slender columns and less ostentatious ornamentation. This architectural form spread through mainland Greece, with the Temple of Athena Nike, at the entrance to the Acropolis in Athens, being an early example and the first Ionic building on the Acropolis.

Knossus is one of the most important sites in European art history, and one of the first studied for many scholars in basic art history. This question is helpful because it teaches while it asks: most students can recall or relate Knossus with the memorable Minotaur, but often do not correlate it with the Bronze Age or with being Europe's oldest city.

The figure at the top of the Column of Trajan is actually St. Peter. It was previously a statue of Trajan himself, but the statue went missing in the Middle Ages. It was replaced with the current bronze statue of St. Peter by Pope Sixtus V in 1587.

Image accessed through Wikipedia Media Commons: https://upload.wikimedia.org/wikipedia/commons/e/e2/RomaColonnaTraiana%26BasilicaUlpia.jpg

Throughout the history of Christian art, Jesus Christ has been depicted in a variety of roles. During the Byzantine era, depictions of Christ as the Pantocrator, or "ruler of the world," were common. Images of the Pantocrator appear at the top or center of Byzantine hierarchical compositions, and are often flanked by angels.

The deep carving on the Hagia Sophia's pillars and in other decoration makes them appear hollow and too delicate to support the cathedral's weight. The close-set windows lining its golden dome's base create the illusion that the dome is floating. Together they suggest that the whole building is supported by some divine power rather than by its own structure. 

The Hagia Sophia was originally built as an early Greek Orthodox church. It is difficult to consider the architecture as of a particular time period or style as it has been changed and influenced so many times. There are, however clear remnants of Greek Classical style as well as the early hints of what will become the Romanesque church style. 

Image adapted from http://www.publicdomainpictures.net/hledej.php?hleda=hagia+sophia+5.

The church is a combination of central and Basilica plan. It has all of the standard additions of those styles, including the nave and apse, as almost every church of this type does. The narthex is identified as the porch-like addition opposite the apse. This church does not have an atrium, however, which would look like a long open plan that sits before the church door.

Image adapted from http://www.publicdomainpictures.net/hledej.php?hleda=hagia+sophia+5.