MEXICO CITY >> As a symbol of heritage and change, the Reforma Tower is a striking affair: a modern 800-foot skyscraper fused at its base with a pink Venetian-style mansion from the 1920s.

It is the latest and arguably most blatant effort to counter criticism from conservationists who have complained that this city is losing its historical charm.

In this case, architects have taken one of the few remaining 20th-century, European-inspired houses on the lavish Reforma Avenue, and slapped a high-rise behind it.

The building, near completion, is expected to be the second tallest in Latin America, behind a 984-foot tower in Chile, and the mansion will serve as a boutique and a cafe for the tower’s office complex.

“I just don’t understand why would anyone want to place an ugly, lifeless office building here, instead of keeping the beauty and identity of the historic mansion,” said Ruben Ochoa, an architect and conservation enthusiast who opposes the steady eradication of Mexico’s historical architecture. “This is an assault to the form.”

The avenue was originally called Empress Boulevard after Carlota, the wife of Maximilian I, who was installed as emperor of Mexico with the help of Napoleon III of France. Now known in Spanish as Paseo de la Reforma, the grand 19th-century avenue serves as a visual metaphor for the city’s complex history and the struggle between holding onto the past and embracing the future.

In the past 50 years, an architecturally eclectic collection of buildings, luxury hotels, banks and shopping malls have replaced almost 90 percent of the mansions on the boulevard. The old mansions had a special name — Porfirian, after the former President Porfirio Díaz, an aficionado of European culture who embraced the transformation of the city’s architecture during his 35-year tenure, which ended in 1911.

Some urban design experts argue that the demolition is not uncommon or bad. World capitals like Mexico City ought to be functional, they say: Modern lives require buildings that meet present needs.

“The city should grow upwards, not outwards,” said Benjamín Romano, the architect who is in charge of the Reforma Tower project. “We must repopulate the center. But we should do so by preserving and integrating old, original spaces with brand-new ones.”

In a flourish, Romano likened the architectural world to the universe, where stars go through their life cycles in a dramatic display and “the image is beautiful.”

“There is nothing wrong with old and new coexisting in the same space,” he said.

Yet others view the obliteration of the city’s European architecture as a disregard for urban style and the preservation of historically valuable property.

“In Mexico, urban design is like a side platter,” said Pamela Castro, a scholar of urban design at the National Autonomous University of Mexico. “No one ever takes it seriously as a discipline.”

After the grand avenue’s construction in the 1860s, a line of emperors, presidents and governors made their mark along it, adding and removing buildings, changing elements of the road, and placing statues and monuments in its broad median strips. The boulevard came to embody Mexico’s social and political life — with all of its nuances, glory and messiness — as much as anything in the capital.

“Paseo de la Reforma is a place that has experienced a series of transformations, where the physical manifestation of the powerful has taken place over time,” Castro said. “First, it was the wealthy aristocratic families building beautiful mansions. Now, it is the business leaders and companies.”

The problem, some experts contend, is that much of the architectural heritage has been torn to pieces to make room for modern buildings without any consideration for urban design or planning.

And the few examples that remain, like the pink granite mansion, have, at best, been stripped of their cultural distinction and, at worst, brutalized.

In the words of Carlos Fuentes, the acclaimed Mexican writer, this is not only a 20th-century phenomenon. Old cities are living and breathing entities, where the future is built not only atop the past, but also beside it. Indeed, the Templo Mayor — which dates to when Tenochtitlan, the capital of the Aztec empire, was established here in the 14th century — sits at the heart of Mexico City today.

“Mexico City, like Rome, is a layered city where past civilizations coexist with one another in order to move forward,” Fuentes wrote in the novel “The Death of Artemio Cruz.”

One such leap took place in the 1950s, when city officials shattered regulations of the Porfirian era, ushering in a building boom. Limits like a maximum height for buildings along Reforma, where structures could not be taller than the palm trees, were tossed to the wind.

The reasons for the change remain unclear. Some argue that in a steadily growing real estate market, it was profitable, while also serving to repopulate the city. Others argue that it reflected a disregard for urban coherence and a disdain for prior aesthetic conventions.

The tension persists today, in various parts of the city. Along the broad Chapultepec Avenue, which is lined by pre-Hispanic aqueducts that still function, the city authorities have planned an enormous outdoor shopping mall as part of an ambitious urban project, sort of a Mexican version of the High Line in New York. The plan elicited criticism from conservationists who saw yet another assault on the city’s architectural integrity and its public treasures.

Today, Reforma holds the highest real estate values in all of Mexico. Its tenants include HSBC, Deloitte Consulting, the Capital Grille and the Mexican stock market. Whatever conservationists think of the skyscrapers, the street remains among the most trafficked and iconic in the capital.

“I think it is a good example of this city’s contrasts and contradictions,” Jaime Bastida, an accountant, said as he walked past the Reforma Tower on a busy morning recently. “It represents us well, however ugly.”

Others, however, have more pressing concerns than architectural integrity.

Lourdes Moreno, 43, a mother of four, works as a janitor in one of the tall office buildings nearby.

“I walk here every day and rarely notice the buildings or the absence of them,” she said. “To be honest, I don’t really have time to think about it.”