Many of these grand projects will have a visible aesthetic effect on Istanbul, which is what infuriates the protesters.

Planners envision a third bridge spanning the Bosporus at a cost of $3 billion, for which ground has already been broken; $10 billion to be spent on a third airport, which would be the world’s largest; and a $2 billion outlay to create a financial center in Istanbul to compete with Dubai and London. On top of a slew of equally large projects in high-speed rail, subways, ports and other amenities, Istanbul is also seen as a leading contender to secure the 2020 Olympic Games.

The decision on the Games will be announced in September, and if Turkey wins, the building and borrowing will only speed up.

To Richard Segal, a credit analyst at the investment bank Jefferies in London, it is the hidden buildup of external debt on the part of Turkish banks and companies that is most worrying. He said it reminded him in some respects of the situations in Ireland and Spain before their collapse.

Ireland and particularly Spain entered the euro crisis with budget deficits and debt levels among the healthiest in the euro zone, the consequence of building booms that lifted tax revenues and allowed governments to spend freely without busting the budget.

As is now the case in Turkey, however, banks and corporations were issuing bonds, many of them short term, at very low interest rates. And like Spain and Greece before 2008, Turkey runs one of the largest current account deficits in the world, at around 7 percent of G.D.P. That, economists say, sets in motion a vicious circle as an overheated economy sucks in imports. That, in turn, creates a stronger currency that hurts the country’s exports, forcing Turkey to borrow ever more to finance the gap.

“This looks like a huge debt bubble,” Mr. Segal said.

He added that Turkey was even more vulnerable than other emerging markets pumped up by hot money in that domestic factors, particularly the possibility that the riots might lead to political unrest, were as likely to send investors fleeing as the wider possibility of an increase in interest rates in the United States, which would also stanch investment flows into emerging markets.