Sitting across from me in Istanbul’s Ataturk Airport 10 days ago was a young woman in a full burqa that left only her eyes visible — along with pink Nikes peeking out from under her robes. The incongruities were not limited to those running shoes, though, for behind her was a huge photo of two nubile, scantily clad and kiss-blowing “angels” gracing the airport’s Victoria’s Secret store.

These juxtapositions frame some of the contrasts that are Istanbul, where on any given street modern Western attire blends with headscarves and also full burqas. Its famed Blue Mosque, with an interior six stories high of stunning blue-and-white decorated tiles and able to accommodate 7,000 worshipers, is one of many gorgeous mosques; yet Istanbul is also a city of churches and synagogues, and even a Jewish museum.

That diversity is, in fact, one of Istanbul’s many strengths, and the encouragement of it was a guiding principle of Mustafa Kemal Ataturk, who ushered in democracy to Turkey in the 1920s, putting his people’s interests ahead of self-aggrandizement right up to his death in 1938. That many Turks highly prize their freedom to be themselves in all of their diversity has been evident over the last month. The issue provoking massive demonstrations was ostensibly a pocket park’s demolition, but as we all know, the issues really extended much more fundamentally to Prime Minister Recep Tayyip Erdogan’s attempts to control his people’s personal lives.

My all-week conference and meetings ended on Friday, and I used my “one short day in the Emerald City” before my return to sightsee: visiting the Blue Mosque, riding trams and buses all over the city, and that evening winding up on Taksim Square. I went there not expecting to get caught up in a demonstration. Once there though, I found myself unable to leave not because I couldn’t, but rather because I didn’t want to.

Police ringed the park, occupying the high ground at all of its entrances and allowing no one in. But that didn’t deter demonstrators from filling the giant square that fronts the park as waves of people materialized, numbering in the thousands. Riot police were visible within the park, and water-cannon trucks lurked on the corners of the square itself looking like our oil delivery trucks but with low, armored skirts and a dozer blade for their front bumper. Some demonstrators placed single red carnations in the grillwork of these trucks, and one even offered a flower to its driver!

Many demonstrators waved flags with “Taksim” on them and also “solidarity” in Turkish and English and Turkish flags with a portrait of Ataturk on them. Chants rose up, accompanied by hand-waving and a kind of up-and-down undulation that would move through the crowd periodically. For all of its size and noise, though, the crowd was orderly.

Things continued this way for about an hour when a police microphone announced everyone had to leave the square. The response was loud booing. The stand-off ended with the movement of about 200 riot police, helmeted and carrying large, clear shields. They assembled themselves into units that looked like an ancient Roman phalanx preparing for battle with the front row keeping their shields straight ahead while the second rank held their shields up and angled back over the first rank to protect from airborne objects, much as the Romans used that same technique for protection against high-arcing arrows. But all that these troops had to face was flying red carnations.

So with the water-cannon trucks right behind them, the riot police advanced, clearing demonstrators back and allowing the trucks to move in to do their very effective driving off of the crowd. However, one truck was not initially protected by police and found itself surrounded by demonstrators who would not let it move. That tactical error was soon remedied, however, with riot police pushing the demonstrators out of the way so the truck could go about its work unimpeded, and by 9 p.m., the square was empty. However, I understand that at midnight crowds assembled there again, and this time tear gas was used.

The experience of watching these demonstrators was moving and powerful. They understood what they risked, but they also knew what they had to lose should democracy give way to autocracy. I returned home, grateful as always to be an American and reminded again that the liberty we celebrate each year at this time and yet so easily take for granted is indeed a precious commodity in precarious supply in so many other nations of the world.

Mr. Hudspeth lives on Glen Hill Road.