Question: Trajan's Column is located in Trajan's Forum, built near the Quirinal Hill, north of which rectangular forum (plaza) surrounded by the ruins of several important ancient government buildings at the center of the city of Rome?

Context paragraphs:
Ulpian Library: The Bibliotheca Ulpia ("Ulpian Library") was a Roman library founded by the Emperor Trajan in AD 114 in his forum, the Forum of Trajan, located in ancient Rome.  was considered one of the most prominent and most famous libraries of antiquity, (the Library of Alexandria of the ancient city of Rome).  Indeed, it was considered the major library in the Western World upon the destruction of the Library of Alexandria in the 3rd century.  “Venantius Fortunatus also writes of ‘Vergil recited in Trajan's forum in the city’ about 576 AD.”  It was the only Roman library to survive until the Fall of Rome in the mid-fifth century.

Basilica Ulpia: The Basilica Ulpia was an ancient Roman civic building located in the Forum of Trajan.  The Basilica Ulpia separates the temple from the main courtyard in the Forum of Trajan with the Trajan's Column to the northwest.  It was named after Roman emperor Trajan whose full name was Marcus Ulpius Traianus.

Forum of Theodosius: The Forum of Theodosius (Greek: φόρος Θεοδοσίου , today Beyazıt Square) was an area in Constantinople.  It was originally built by Constantine I and named the Forum Tauri ("Forum of the Bull").  In 393, however, it was renamed after Emperor Theodosius I, who rebuilt it after the model of Trajan's Forum in Rome, surrounded by civic buildings such as churches and baths and decorated with porticoes as well as a triumphal column at its center.

Trajan's Market: Trajan's Market (Latin: "Mercatus Traiani" , Italian: "Mercati di Traiano" ) is a large complex of ruins in the city of Rome, Italy, located on the Via dei Fori Imperiali, at the opposite end to the Colosseum.  The surviving buildings and structures, built as an integral part of Trajan's Forum and nestled against the excavated flank of the Quirinal Hill, present a living model of life in the Roman capital and a glimpse at the restoration in the city, which reveals new treasures and insights about Ancient Roman architecture.

Roman Forum: The Roman Forum, also known by its Latin name Forum Romanum (Italian: "Foro Romano" ), is a rectangular forum (plaza) surrounded by the ruins of several important ancient government buildings at the center of the city of Rome.  Citizens of the ancient city referred to this space, originally a marketplace, as the "Forum Magnum ", or simply the "Forum ".

Vicus Longus: The vicus Longus was a street in Regio VI of ancient Rome, linking the Suburra to the summit of the Quirinal Hill along the valley between the Quirinal Hill and the Viminal Hill.

Roman Forum (Plovdiv): The Roman forum of Philippopolis (Latin: "" ; Bulgarian: Римски форум на Пловдив , "Rimski forum na Plovdiv") is a rectangular forum (plaza) surrounded by the ruins of several ancient administrative buildings at the center of the city of Plovdiv.  It was the center of public, administrative, commercial and religious life in the ancient city.  Meetings, discussions, celebrations and state events were held there.

Trajan's Column: Trajan's Column (Italian: "Colonna Traiana" , Latin: "COLVMNA·TRAIANI" ) is a Roman triumphal column in Rome, Italy, that commemorates Roman emperor Trajan's victory in the Dacian Wars.  It was probably constructed under the supervision of the architect Apollodorus of Damascus at the order of the Roman Senate.  It is located in Trajan's Forum, built near the Quirinal Hill, north of the Roman Forum.  Completed in AD 113, the freestanding column is most famous for its spiral bas relief, which artistically describes the epic wars between the Romans and Dacians (101–102 and 105–106).  Its design has inspired numerous victory columns, both ancient and modern.

Quirinal Hill: The Quirinal Hill ( ; Latin: "Collis Quirinalis" ; Italian: "Quirinale" ] ) is one of the Seven Hills of Rome, at the north-east of the city center.  It is the location of the official residence of the Italian head of state, who resides in the Quirinal Palace; by metonymy "the Quirinal" has come to stand for the Italian president.  The Quirinal Palace has an extension of 1.2 million square feet.

Horse Tamers: The colossal pair of marble "Horse Tamers"—often identified as Castor and Pollux—have stood since antiquity near the site of the Baths of Constantine on the Quirinal Hill, Rome.  Napoleon's agents wanted to include them among the classical booty removed from Rome after the 1797 Treaty of Tolentino, but they were too large to be buried or to be moved very far.  They are fourth-century Roman copies of Greek originals.  They gave to the Quirinal its medieval name "Monte Cavallo" (), which lingered into the nineteenth century.  Their coarseness has been noted, while the vigor—notably that of the horses—has been admired.  The Colossi of the Quirinal are the original exponents of this theme of dominating power, which has appealed to powerful patrons since the seventeenth century, from Marly-le-Roi to Saint Petersburg.

Supporting paragraphs: Trajan's Column Roman Forum
Answer: Roman Forum