Believed to date back to 740, Vienna's oldest church is an impressive sight. Its tower is composed of 12th century stonework and its roof dates back to the 15th century. The west side of the church is flanked by an iron Renaissance door from the 1530s, while the exterior walls of the building are covered in ivy during the summer months. Inside, the sleek Romanesque nave of the 12th century can be viewed, but note that the church is closed to the public on Sundays due to religious services.