Doors Open Milwaukee returns for its second year on Saturday and Sunday, Sept. 22-23, throwing open the doors to dozens of Milwaukee buildings to allow the public to glimpse rarely seen spaces.

Last year's event was a smash success. One venue I visited, the observation deck of the U.S. Bank building, has been closed to the public for decades and drew a seemingly endlessly regenerating line of eager gawkers.

This year, the free event includes more than 120 buildings in the Downtown area and beyond and a couple dozen tours, too.

A complete list of venues, plus maps and other useful information can be found at Historic Milwaukee's Doors Open Milwaukee website.

In the meantime, since you can't likely get to all 120 places in two days, here are 10 places I recommend checking out. Add yours using the talkback feature below.

• Recently, I climbed the tower at City Hall and I suggest you do the same. You need a ticket for the tower tour, but even if you decide not to do that, be sure to visit the Common Council chamber in Henry Koch's towering symbol of Milwaukee.
• We were also lucky enough to get to the very top of the Allen-Bradley clocktower. You won't go quite as high, but you can get a rare look at the view from the comfy 17th floor observation room in the tower.
• One of the scariest climbs I've taken has been to the top of the St. Josaphat dome. You can visit the church, which is marvelous, on a self-guided tour. You can't however, take this trip. 
• The Brewhouse Inn and Suites doesn't open at the old Pabst Brewery until early next year, so this visit will offer a nice sneak preview. I can't wait to see those giant copper brew kettles get a new life.
• The Chudnow Museum of Yesteryear is the city's newest history museum and you definitely ought to check it out for its range of Milwaukee memorabilia, presented in a Streets of Old Milwaukee-style setting.
• I always used to think the City Lights building in the Valley would make an amazing concert venue. Instead, the Zimmerman folks have moved their architecture studios in there. It appeared recently on Italian television and it's not fair that folks in Pescara have seen it but you haven't. Plus, the local AIA chapter will have more than 10,000 Lego blocks on hand for the kids to enjoy (bring the hand sanitizer)!
• Recently I wrote about some great Romanesque architectural treasures in Milwaukee and one of the most grandiose is the Federal Courthouse on East Wisconsin Avenue. There are interior-only and exterior-only tours on offer during Doors Open. Do 'em both.
• A group of Milwaukeeans is working hard to buy, restore and preserve Frank Lloyd Wright's row of American System-Built homes on Burnham Street. You can gain entry into a fine example of one of them during the event.
• Surely, you know by now that I am a complete and utter old schoolhouse geek. In fact, I had hoped to offer a tour of an old schoolhouse during the Doors Open weekend. Alas, it will happen at a different time, but in the meantime, you can get inside to take a look at Golda Meir School, previously Fourth Street School, in Brewers Hill. The building is one of a pair of matching buildings (the other is Kagel, formerly Mineral Street, in Walker's Point) designed by Henry Koch at the beginning of the 1890s.
• St. Paul's Episcopal Church on Knapp and Marshall has a bit of everything: a building designed by Edward Townsend Mix, a huge collection of original Tiffany windows, a Schantz organ, Cyril Colnik ironwork and a newly restored 16th century Flemish tapestry. How can you resist?

There's so much more on offer, you can hardly go wrong! Kudos to Historic Milwaukee Inc. for doing this incredible event again.