Five blocks from the Vatican, on the bustling, tourist-packed street leading to St Peter's Basilica, a Taiwanese flag flutters from the window of a third story suite of offices that house Taipei's embassy to the Holy See.
These days, the staff inside are anxious. They know that one night they may have to lower that flag - red and blue with a white sun - for the last time.
As the Vatican and China move closer to a historic deal on the appointment of bishops, which would signal a warming of once-frigid relations, diplomats and scholars say Taiwan could lose the most from the deal.
Under the deal, the Vatican will have a say in negotiations for the appointment of future bishops in China, whose Catholics are divided between an "underground" Church loyal to the pope and a government-backed Church.
Even a partial resolution of the issue could open the way for eventual diplomatic relations between Beijing and the Vatican. That would give the Church a legal framework to look after all of China's estimated 12 million Catholics.
It would also leave Taiwan in the diplomatic lurch.
The Vatican is one of only 20 states that still recognise Taiwan, officially known as the Republic of China. Beijing insists that if countries want relations with it they must break ties with Taiwan.
The Chinese Foreign Ministry said last month that China had always been sincere in its efforts to improve China-Vatican relations.
A senior Vatican official said however that the accord on bishops "is not a political one," suggesting that it does not include any formal link to diplomatic relations and that the Vatican will not be the next country to switch relations to China from Taiwan.
Some experts say diplomatic ties between Beijing and the Vatican are inevitable, even if probably not right around the corner.
"The Church does not have preference among its children and it's clear that the Vatican does not want to do anything to displease Catholics on Taiwan" said Agostino Giovagnoli, a history professor at Milan's Sacred Heart Catholic University and the author of two books on Catholicism in China.
"But strategically the Catholics on the mainland are more important because the future of evangelisation of China and all Asia passes through China. It is key for the Catholic Church," he told Reuters.
While Taiwan's embassy to the Vatican proudly flies the flag from its window, hosts cultural events and publishes a newsletter, the Vatican's counterpart in Taipei is a study in low-key diplomacy.
It is located in a quiet residential neighbourhood in the city's Daan distinct. The only clue of its function is the papal stem of crossed keys and a tiara, or crown. That symbol is not widely known to the general public.
The Vatican's last diplomat on the mainland was expelled in 1951 and the Holy See mission settled in Taiwan, to where Chiang Kai-shek's Nationalist government fled in 1949 after its defeat by the communist armies of Mao Zedong, founder of the People's Republic of China (PRC).
Since the 1970s, following the United Nations vote to recognise the PRC as the sole legal China, the Vatican has not appointed a nuncio, or ambassador, to Taiwan. It has kept the status of the mission at the lower level of "charge d'affaires ad interim" since.
Diplomats say the Vatican's low profile in Taiwan for four decades has been aimed at placating Beijing, which still sees Taiwan and its sacred territory.