That's the belfry of St. Augustine Parish in the town of Bantay in Ilocos Sur. Though Bantay isn't part of Vigan City, many people also consider this place as part of Vigan as the church is just outside of the city, and is one popular landmark for tourists to visit.
The belfry was quite far from the church and is situated atop of a hill because during the rule of Spain in the Philippines centuries ago, Filipino rebels would use this belfry as their watch tower. Actually, the word "bantay" means two things: in Tagalog it means, "to watch," and in Ilocano (the dialect of the people living in this part of the country), it means "mountain." Both translations fit this belfry really well. :)
Tourists can coordinate with the tourism council should they want to enter the belfry. If you happen to travel in this part of the Philippines, I really recommend you to enter and climb to the top of the belfry, where you can see a panoramic view of the area.