OnMilwaukee.com’s managing editor Bobby Tanzilo has been exploring Milwaukee in-depth and behind the scenes via his ongoing Urban Spelunking series for a few years now, and he’s written more than 70 articles and blog posts.

Those stories have taken him to the top of St. Josaphat’s and City Hall, out to the Breakwater Lighthouse, and down into tunnels beneath the South Side and through the rubble of collapsed buildings to see long-idle beer storage caves.

Now a couple dozen of these pieces have been updated and expanded and collected into a book. "Hidden History of Milwaukee" is Tanzilo’s third book for the South Carolina-based local history publisher, The History Press.

Tanzilo has also published a trio of books in Italy on emigration.

"Hidden History of Milwaukee" hits shops on Tuesday, May 6, so we asked Bobby about the book and the ongoing series that can be read at OnMilwaukee.com.

OnMilwaukee.com: How did you pick the stories to be included in the book?

Bobby Tanzilo: There were definitely more that I’ve done than could fit into the book, so I had to look back and go through and pick the ones I thought would work best. And I tried to have a balance of different kinds of places: churches, landmarks, schools, etc.

OMC: Was it hard to choose?

BT: It wasn’t always easy. I did include a few that I later replaced. And the hardest part was that, even when the book was in production, I continued to visit places and write articles and blogs about those places, but I couldn’t include them. I’ll guess I’ll have to consider a volume two. Though, of course, you can read them online at OnMilwaukee.com in the meantime.

OMC: Do you have a favorite in the book? What about the ongoing series – any favorites there?

BT: I have a few favorites. I really enjoy seeing places that you can’t typically get into. So, the Breakwater Lighthouse was cool, especially because we can all see, but almost none of us has ever gotten to go inside. And really, I like learning about and seeing things I didn’t expect.

Like on the lighthouse one, for example, meeting the Coast Guard folks and hearing their stories and about their jobs was, really, even more interesting than seeing the lighthouse itself.

And when I visited the Milorganite plant on Jones Island I learned after well over 30 years that the smell I always associated with summer visits to my grandparents’ Walker’s Point backyard is the smell of Milorganite production.

OMC: How did you get started doing these kinds of stories?

BT: It just kind of happened. I’d done a few here and there, not with any expectation of it becoming anything like a series. Then, in relatively quick succession, I got invited to the lantern atop St. Josaphat’s, the City Hall bell tower and to go up onto the "wings" of the Milwaukee Art Museum. At that moment, it just became almost an addiction, or a quest.

OMC: How do you decide which places to visit and write about?

BT: All kinds of ways. Now that I’ve been doing it, I get a lot of invitations. Sometimes, like when I write about the carpentry work in the attics of old schools, it just comes out of visits to places where I stumble upon things that really catch my eye. Other times, I just spot places. I love the Milwaukee landscape because there is so much to see. You just have to look. Then I make an effort to get inside, where more often than not, I learn interesting things I had no idea about.

One day, I went over to St. John’s Lutheran Church on 8th and Vliet to see if I could get a peek inside, but every time I went there it was locked. On this day, I noticed another steeple and I went to investigate. That church was open and the secretary gave me a tour. Despite having lived here 30 years, that was the first time I’d seen St. Francis of Assisi. When I left there, I noticed another steeple up 4th Street and I found Trinity Evangelical and I spent a few months working on getting in there.

That day, I didn’t get into St. John’s – though I have since – but I did learn about St. Francis and its links to the Civil Rights movement here, and it led me also to Trinity, which once had a huge congregation and made national news in the 1890s when the pastor married a black man and a white parishioner.

OMC: Any upcoming ones you can tell us about?

BT: Well, I’m always doing them and looking for more to do, but I don’t want to spoil the element of surprise.

OMC: What’s your dream place to visit in Milwaukee?

BT: There are a few. I really want to climb the North Point Water Tower and get a look inside the Linnwood Water Treatment Facility, but they are off-limits to the public. I hold out hope.

Because I’m an old school geek and I’ve been getting more and more interested in St. Stephen’s Lutheran Church and School in Walker’s Point. Try as I might I can’t seem to get a peek into the school.

OMC: Are there any events to promote the book in town?

BT: Yes, I’ll be at Boswell Books at 7 p.m. on Wednesday, May 21, and I’ll be at Costco in Pewaukee, signing books from 2 until 4 p.m. on Saturday, May 24. Come early and you can make a lunch by going from sample stand to sample stand and then I’ll sign a book for you.