One of two churches in Venice dedicated to Mary Magdalene (the other is on the island of Guidecca), this Cannaregio church was founded in 1222, but the one we see today dates from an 18th century rebuilding over top of the medieval church.
It’s a Neoclassical church, round on the outside and hexagonal inside. There was some resistance towards round churches in Venice (Palladio’s plan to build the Redentore round was squashed), but that all changed after Santa Maria della Salute when "round" came into vogue in a big way.
The architect was Tomaso Temenza, a scholar and historian of Venetian architecture who built very few buildings. La Maddalena was built in 1760-89 and was a parish church for a few decades. The Venetian Republic fell to the French, the church was closed in 1820, and then at some point in the 19th century, a demolition order was issued. Gianantonio Selva (Temenza’s student and the architect who built the opera house La Fenice) fought the order and saved the church, but its bell tower was demolished in 1881.
For a while the church was an oratory used for weddings and today, it’s open occasionally for exhibitions. When I visited it several years ago, some kind of business convention was going on inside. In December 2008, the church hosted a collection of nativity scenes/crèches/presepi from all over Italy, including an amazing one in which the Nativity takes place in an incredible miniature Venice. You can see it here on YouTube (thanks to A Lover of Venice for the link).
Most recently, the church was used as an exhibit hall for Le Biennale 2009. Blog friend AnnaLivia took some great photos of the interior (love the contrast between the architecture of the church and the modern art on display).