Today’s column is a continuation of my series. If you’d like a handout of the entire series along with accompanying photos, send me an email.

We were last in Classical Greece. Alexander the Great’s conquests had reached Egypt, Europe, the Middle East, and part of Asia. The period from his death in 323 BC to 31 BC is known as the Hellenistic era. (“Hellas” is Greek for Greece). During this time, Egypt’s city of Alexandria had flourished in commerce, education, philosophy, and art. The Ancient Library of Alexandria was the center of literary works in the world.

The Hellenistic Age came to an end with the rise of the Roman Empire. Although Julius Caesar’s army burned the Library of Alexandria, the Romans went on to absorb Greek culture, art and architecture and became innovators in their own right. They developed new construction techniques and materials and built new structures such as basilicas, triumphal arches, aqueducts, amphitheaters, and grand highways.

The Romans introduced the arch to architecture (an earlier Etruscan idea). The arch has far greater capabilities than the Egyptian and Greek lintel because it can span eight times the distance of a stone lintel. The arch quickly led to domed ceilings, and because arched and domed structures can share weight evenly, they were soon used throughout the city.

Arches were also used to build aqueducts, which provided Rome with water from far away sources. The arch, the vault (basically a deep arch) and the dome (a collection of arches) of the 1st century BC are the greatest achievement in Roman architecture.

The roof of the Pantheon in Rome, commissioned by Hadrian in 120 AD, and a hot tourist destination, is the most notable example of Roman genius. Not only is the span of the dome impressive, but its center is open to the sky.

Wealthier homes were typically built around atriums. Interiors were made of painted plastered walls and mosaic floors. Many houses had pipes that carried water into the home and also acted as underground heating systems.

The Romans used finely ground volcanic lava as their mortar in place of clay. This was the strongest concrete in history until the development of Portland cement. When fortified with volcanic rubble, the concrete was sturdy enough to build their great arches, aqueducts and roads. Concrete was also cheaper than solid stone and could be given a more presentable façade using stucco, marble veneer, fired brick, or terracotta.

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The Romans also came up with the concept of the basilica as a place for large gatherings where one side was built alongside a city’s marketplace and enclosed by colonnades. Basilicas were later adopted by the Christian church.

Roman baths were displays of breath-taking interiors built with arches, domes, vaults and buttresses. They were often huge, symmetrical complexes that included pools, fountains, steam rooms, and even libraries, lavish with marble, statues, and mosaics.

Roman theaters were inspired by those of the Greeks and displayed their penchant for enclosing spaces with complete or partial roofs or canvas awnings. The Colosseum, built from 72 AD to 80 AD, is the largest and most famous of Roman amphitheaters and was copied throughout the Empire.

The triumphal arch is another Roman invention. It had no practical function other than to commemorate significant events such as military victories. Early examples marked thoroughfares with single, double or triple entrances.

Alas, the Romans could be triumphant for only so long. What follows their demise? That is my next column.

Patti L Cowger is a Napa-based interior designer and owner of PLC Interiors. For more information about her design services, visit her website at call (707) 322-6522; or email Demystifying Design appears every other Saturday.