The Roman Forum (Forum Romanum) was originally a market place but became a place for politics, and public and private business. The Forum Romanum was located in the area between the Palatine and Capitoline that was surrounded with temples and public buildings. Money-changers operated in the forum. Besides the Forum Romanum, other fora (fora is the plural of forum) grew up in Rome.
The Servian Wall (Murus Servii Tullii) was supposedly constructed by King Servius Tullius in the 6th century B.C. but is thought, on the basis of archaeological study of the building material, to date from 378 B.C., instead.
The cloaca maxima was the sewer system built in the sixth or seventh century B.C., by one of the kings of Rome -- probably Tarquinius Priscus, although Livy attributes it to Tarquin the Proud -- to drain the marshes in the valleys between the hills into the Tiber River.
It is claimed Trajan, Hadrian's adoptive father, had not wanted Hadrian to succeed him, but was thwarted by his wife, Plotina, who covered up her husband's death until she could make sure of Hadrian's acceptance by the senate. Hadrian was the emperor of Rome from A.D. 117
-138.
Circus - The Roman Racetrack Arena - Circus and the Circus Maximus
King Tarquin laid out an arena (arena comes from the Latin for sand: harena) known as the Circus Maximus. Down the center was a barrier (spina), with pillars at each end around which charioteers had to maneuver -- carefully. Julius Caesar enlarged this circus to 1800 feet in length by 350 feet wide
Colosseum - Flavian Amphitheater
The amphitheater (from the Greek amphi ~ on both sides and theatron ~ semicircular viewing place or theater) was developed as an improvement over the the Circus Maximus for gladiatorial combats, wild beast fights (venationes), and mock naval battles (naumachiae).
Thanks to the August 24, A.D, 79 eruption of Mt.Vesuvius, we have samples (from the area of Italy known as Campania) of how wealthy Romans decorated the interior walls of their homes, and thanks to De Architectura, by Vitruvius, and Pliny the Elder's Natural History, we have descriptions of the technique of the fresco.
