Basilica di San Marco (St Mark's Cathedral) is magnificent. It is both a wonderful architectural flurry of Gothic, Byzantine, Romanesque and Renaissance styles declaring the wealth of Venice over centuries, and a spiritual place of worship. Its domes and turrets, and gold mosaic stand out over the square and over Venice, and four ancient classical horses top the entrance, taken from Constantinople (Istanbul) when Venice sacked that city around 1200. Inside the church is dazzling.
The church was begun in 828 when the body of St Mark was returned to Venice, smuggled by merchants from its resting place in Alexandria, Egypt. An angel had told St Mark his final resting place would be Venice (which did not even exist at the time) and the Venetian leaders were keen to make it happen. Over the years, churches were built, burnt, rebuilt and expanded resulting in the incredible building we see today.