Speaking of over the top, is this not the best example?
The garish former church (now a museum) has a steeple that is 81m (265 ft) high. The bell tower on the left has 144 individual mosaic coats of arms representing provinces, cities and towns of the Russian empire that reflected grief over the murder of Czar Alexander II.
Photos of the interior are below the text. The walls and ceilings are covered with mosaic paintings. some 8000 square yards in all, with nary an inch left un-decorated. The interior of the church has multi-colored marble from Italy and colored stone from different regions of Russia including Ural jasper, porphyry, violet gray Altai jasper, dark red, pink and green marble.
The building commemorates the assassination of Czar Alexander II in 1881. It was built from 1883 to 1907 under Nicolas II. There is a canopy erected over the spot of the assassination. Not baroque like so much of St Petersburg, this style has its origins in medieval Russian architecture. It is similar to 17th-century churches in Yaroslav, northeast of Moscow and a World Heritage site, as well as St Basil’s Cathedral in Moscow. The spheres atop the spires stand out against any sky and are as far out as anything you might see at Familia Sagrada, for example, if even more demanding of attention.
The interior mosaics were painted by Vladimir Belyaev, Nikolay Kharlamov, Andrei Ryabushkin https://en.wikipedia.org/wiki/Andrei_Ryabushkin, Nikolay Koshelev https://en.wikipedia.org/wiki/Nikolay_Koshelev, Nikolay Shakhovskoy, Alexander Novoskoltsev, and others.
After WWII the cathedral was used by the Maly Opera Theater for storage. There were broken windows, holes in the roof and the cupolas. Restoration began in 1980.
Here’s an interesting use of light:
This is a world treasure and a must visit!