In 2010, the very impressive Uspenski Cathedral (Cathedral of the Assumption) was constructed and consecrated on the site of an earlier destroyed temple overlooking the Volga river, near the stone that marks the spot where Yaroslav the wise is said to have founded the city. The cathedral cost approximately 20 million Euros to complete. The Cathedral is about 2000 square meters in area and is approximately 60 meters high.
As with all Russian Orthodox holy churches, women are expected to cover their heads with a scarf (or something similar) when visiting.
Here are some photos of the Uspenski Cathedral: