The Votivkirche (Votive Church) is a neo-gothic church in Vienna, Austria. It was being remodeled when I was visiting, but much of the cathedral was still accessible. The church was built as a thanks to God when the Austrian Emperor Franz Joseph survived an assassination attempt in 1853. His brother helped raise the funds and it was dedicated in 1879. The church was badly damaged during World War II and has had various renovations since then. Wikepedia has some detailed information on the interior as well.
Notre Dame du Sablon (Church of Our Blessed Lady of the Sablon) is a Brabantine Gothic style church in the historic area of Brussels, Belgium. Initially this was the site of a smaller chapel honoring Mary, but around 1400 the construction of the church began and took about a hundred years. The two chapels were added in the 17th century (St. Ursula – 1676, Saint Murcouf-1690) and a significant restoration was needed in the late 19th century due to deterioration. Wikipedia has a fairly thorough summary of the history of the church.
This church is a little older than the average. Saint Vitus Cathedral is in central Prague and is the third church on this site. Construction of this gothic cathedral started in 1344 when the the King of Bohemia wanted a church for coronations, royal burials, and a treasury for the most valuable relics of the kingdom. Work on different parts of this massive church continued at various times over the next 600 hundred years and was considered finally finished in 1929. There is a lot of history online with more details and a virtual tour on the church’s website. In 1997 the church was rededicated as the Metropolitan Cathedral of Saints Vitus, Wenceslaus and Adalbert.