In the United States, June 14th is celebrated as Flag Day, recognizing the day in 1777 when the Second Continental Congress adopted the "stars and stripes" flag. Admittedly this is one of the lesser known patriotic holidays, and is followed a few days later by the even lesser known Juneteenth. (That day, June 19, commemorates the day in 1865 when Black slaves were emancipated in Texas, the largest of the Confederate states.) But I, the social studies teacher and urban historian, am fond of these minor patriotic celebrations and feel it's my responsibility to talk up these dates.And this year on June 14th I also took on a different kind of historian role, as the guide to a bicycle tour in my beloved Brooklyn, New York. I shepherded a group of 12 people on a tour that I called the 2nd Annual Brooklyn Lost Synagogues Bike Tour. Based upon my research on "lost synagogues," buildings that formerly houses shuls, and my first book in the Avotaynu series titled The Lost Synagogues of Brooklyn (2009), I led a group of people interested in learning about Jewish Brooklyn history.We met at the plaza area of the renowned Brooklyn Museum, where on the northeastern section of its campus there is a fanciful fountain and a set of curved steps. Easily recognizable and situated half a block away from a parking lot, this was a good meeting place. A dozen hardy bicyclists including my friend Harold, who has spearheaded a similar shuls study in Newark, New Jersey (and a survey of memorial plaques in Newark and its nearby suburbs) came together and I gave them a briefing about what we would ride to see.I informed the group that we would bike around parts of the Brooklyn neighborhoods of Prospect Heights, Crown Heights, Brownsville and East Flatbush, and see nearly 20 former synagogue buildings. We would also have the chance to visit inside a few of them. I gave some background information about these congregations, whose buildings ran the gamut from large and opulent to modest and crumbling. I also mentioned that the tour was part of the Brooklyn Jewish Historical Initiative, the BJHI, which seeks to highlight the history of Jewish Brooklyn. Most of the BJHI activities so far had been either lectures and panels, or a few holiday celebrations; this bike tour was the first of its type. However, last year I gave a different version of this bike tour (hence this is the "2nd Annual") going into other neighborhoods, with the 5BBC, the Five Borough Bike Club.So the 12 riders and I, who ranged in age from their 20s through their 60s, and evenly split by gender, biked to several former shuls, as well as a former Jewish hospital (the Brooklyn Jewish Hospital on Prospect Place, which is now a residential complex) and a long-ago Yiddish theater called the Parkway (on Eastern Parkway) where my dad had seen a Yiddish-language version of Shakespeare's "King Lear." The majority of these buildings we visited were pre-WW2 constructions, but the one post-WW2 era shul building, on Kings Highway, is now an alternative public high school sporting a vaguely psychedelic mural on its front. However, most of the former synagogues have been turned into Christian churches, a trend I have analyzed and documented in depth.For instance, we saw the still-gorgeous former Shaari Zedek on Kingston Avenue, a huge corner building with the congregation's name rendered in both Hebrew and English carvings. It has been a Baptist church for decades, although a tiny remnant of Shaari Zedek lives on in another Brooklyn synagogue in a different neighborhood. Shaari Zedek was one of at least two lost synagogues we saw that were Conservative; all the others had been Orthodox traditional congregations. One of the former shuls, Adath Yeshurun, was actually built as a theater, turned into a shul, and then turned into a church.There was even one lost synagogue we stopped by on Sterling Place which I do not have a name for, despite my many efforts to locate its name. The front staircase has a metal Jewish star incorporated into a design, which I pointed out to the tour group, and a trapezoid-shaped staircase that is common to many older synagogues found throughout NYC.Some of the riders had additional pertinent information to share with the group, which I appreciated. There is always more we can learn about these sites. Thus this tour had a fascinating if bittersweet tone to it. A lesson I can impart to you all, if you don't already know it, is to record your memories so that future generations will have archives to plumb. Ride on!