Buildings and monuments influenced by Roman Architecture

Altare della Patria, Rome Photo: Alvesgaspar/Wikimedia Commons
Altare della Patria ("Altar of the Fatherland") is a monument built to honor the first king of the newly unified Italy, Victor Emmanual. The monument was designed by Giuseppe Sacconi in 1885.
The final structure was inaugurated in 1911 and construction was completed in 1925. It is built in the neoclassical style and incorporates Corinthian columns, fountains, equestrian statues of Victor Emmanual and statues of the goddess Victoria riding quadrigas.
Its enormous size of the monument has had its fair share of criticism both for its conspicuousness, size, and pompous design. Its construction also destroyed large parts of the ancient Roman Capitoline Hill.

Arc De Triomphe, Paris Photo: Dietmar Rabich/Wikimedia Commons
The Arc De Triomphe is probably the world's most famous Triumphal Arch and one of Paris's most iconic landmarks. It stands at the western end of the Champs-Élysées at the center of Place Charles de Gaulle.
It was built to honor those who fought and died during the French Revolution and Napoleonic Wars. The names of notable French victories and generals are inscribed on its inner and outer surfaces. After the conclusion of the First World War, the Tomb of the Unknown Soldier was added beneath its vaults.
The arch's design epitomizes Neoclassical design and was the work of architects Jean Chalgrun and Louis-Etienne Hericart de Thury. It was directly inspired by the Roman Triumphal Arch of Titus in Rome.
It was designed in 1806 and inaugurated in 1836. The Arc de Triomphe was the tallest triumphal arch in the world until the completion of the  Monumento a la Revolución in Mexico City in 1938.

Brandenburg Gate, Berlin Photo: Pedelecs/Wikimedia Commons
The Brandenburg Gate in Berlin is a fine 18th Century example of neoclassical architecture built by the Prussian King Frederick William II. It was commissioned to celebrate the conclusion of the Batavian Revolution.
Today it is one of Germany's best-known landmarks and one of the finest triumphal arches in the world. It is built on the site of the former city gate that used to mark the start of the road from Berlin to Brandenburg an der Havel.
Construction began in 1788 and was concluded in 1791. The entire structure was designed by architect Carl Gotthard Langhans.
Since its construction, the gate has been the site of major historical events in Germany. It is now considered, rightfully or wrongly, a symbol of the tumultuous history of both Europe and Germany. 

British Museum, London Photo:Ham/Wikimedia Commons
The main core of the British Museum was designed by the architect Sir Robert Smirke in 1823. It consists of a quadrangle with four wings at each of the four main compass point directions.
The building was finally completed in 1852 and now includes galleries of classical sculpture and Assyrian antiquities. Smirke was heavily influenced by classical antiquity including Roman Architecture. 

Buckingham Palace (Eastern Wing), London Photo: Diliff/Wikimedia Commons
Buckingham Palace, as known today, is an amalgamation of various building phases onto an original townhouse built in 1703. The biggest phase of construction was carried out by architects John Nas and Edward Blore during the 19th Century. These consisted of the construction of three wings around a central courtyard.
Buckingham Palace became the official London residence of the British Monarch in 1837.
The last major structural additions were made in the late 19th and early 20th Centuries. These included the East elevation that closed of the courtyard and includes the famous balcony where members of the Royal family congregate to greet crowds.
This wing underwent remodeling work in 1913 by architect Sir Aston Webb to its current form.

California State Capitol, Sacramento Photo: Andre m/Wikimedia Commons
The California State Capitol houses the bicameral state legislature and the office of the governor of the state of California. It is located in Sacramento and is a fantastic example of Neoclassical architecture.
Designed by architect M. Frederic Butler it was built between 1860 and 1874. The building's design is actually based on the of the Capital building in Washington D. C.

Galata Tower, Istanbul Photo: Jorge Láscar/Wikimedia Commons
Galata Tower, Galata Kulesi in Turkish, or the Christea Turris (Tower of Christ by the Genoese) is a medieval stone tower in Istanbul. It is located just to the north of the Golden Horn's junction with the Bosphorus.
It is one of this ancient city's most iconic and striking landmarks and a popular tourist attraction. The Tower is nine-stories tall at a total height of 66.9 meters.
At the time of its construction in 1348, it was the tallest construction in the city. It is built in the Romanesque style and was erected during the expansion of the Genoese colony in Constantinople.
Although the original Architect's name has been lost to history it was repaired by the Ottoman architect, Hayreddin in 1509 following heavy damage from an earthquake.
When the city was captured by the Ottoman's, the tower was modified as an observation tower for spotting fires in the city. Today it has a restaurant and cafe at its upper levels which provide unparalleled views of the city and river Bosphorus.

Horse Guards, London Photo: Alistair Wettin/Wikimedia Commons
Horse Guards is one of the most famous and historic buildings in London. Construction began in 1750 and the building was completed in 1759.
It was originally built as a barracks and stables for the British Household Cavalry but later became an important military headquarters for the British Army.
Horse Guards originally served as the entrance to the Palace of Whitehall, later St James's Palace. It is for this reason that it is still ceremonially defended by the members of Queen's Royal Guard (Queen's Life Guard).
It was designed by William Kent, John Vardy, and William Robinson and was inspired by the fashionable Palladian style at the time.

The Leaning Tower of Pisa, Pisa Photo: Saffron Blaze/Wikimedia Commons
The tower is actually the campanile (free standing bell tower) of the neighboring Pisa Cathedral. Although it is most famous for its tilt, the tower is actually a great example of late Italian Romanesque architecture.
It was designed by Bonnano Pisano and ground was broke in 1173. Construction of the tower would occur in three stages over 199 years until its completion in 1372.
The tower's tilt began as soon as construction reached the second floor, starting a battle of wits with gravity that would continue to the present day. Galileo Galilei would famously use the tower for some of his experiments and it was used by the allies in WW2 as an observation post.

The Reichstag, Berlin  Photo: Taxiarchos228/Wikimedia Commons
The Reichstag, officially Deutscher Bundestag - Plenarbereich Reichstagsgebäude, is an iconic edifice in Berlin, Germany. It was designed by Paul Wallot and was built between 1884 and 1894.
The building was initially intended to house the German Diet, a purpose it fulfilled until 1933 when it was severely damaged during the infamous Reichstag Fire. After the conclusion of WW2, the building fell into disuse.
The ruins were made safe in the 1960's and were only fully restored in the early 1990's after German reunification. 

The Smithsonian Institution Building, Washington D. C.  Photo: Diliff/Wikimedia Commons
Completed in 1855, The Smithsonian Institution Building is built in Seneca red sandstone in a faux Norman style. This is a combination of Romanesque Revival and Gothic styles.
It was the winning entry of James Renwick Junior in 1846 nationwide held competition for its design. It was originally meant to be built in white marble and then in yellow sandstone but the designers and building committee finally settled on Seneca sandstone.
The change in materials was due to it being less expensive than marble and very easy to work.
It underwent a general renovation in the late 1960's to install modern electrics, elevators, heating, ventilation, and air conditioning. Today, the building houses the administrative offices for the Smithsonian.

The White Tower at the Tower of London, London Photo: Bernard Gagnon/Wikimedia Commons
The Tower of London is another British example of Roman Architecture inspired design. It is, in fact, a historic Norman castle keep (donjon) built over several phases from the 11th to 14th Centuries.
The conquering Normans would quickly begin making their mark in Britain with their own take on the Romanesque style, sometimes referred to as Norman Romanesque.
The Tower of London, specifically the White Tower, would be one of their greatest works. Construction began in the early 1080's and it would be extended over time.
It was originally used to provide accommodation for the King and his entourage but also served as a private chapel. The Chapel of St. John in the Tower has superb examples of the rounded Romanesque arch.
Henry the III would later order it to be whitewashed in 1240.

Source: 21 Famous Buildings and Monuments Influenced by Roman Architecture