The Church of El Salvador – Iglesia El Salvador – is a lovely building situated opposite the Balcón de Europa and close to what used to be the Guards Tower.
It was erected in 1505, although the existing structure was not built until 1697, and was then further extended during the period 1776 – 1792.
The interior of the church is well worth a look. You can see a video of both the exterior and interior of the church here: Iglesia El Salvador.