Historic. Located along a walkway behind the main cathedral, this restaurant is housed in a building that dates to the 1700s. The entrance is adorned with carved stone mermaids, hence the 'Sirenas' name. Authentic Mexican dishes are best enjoyed on the third-floor terrace, which overlooks the back of the cathedral. The restaurant closes early, at 7 p.m., on Sunday. Smoking is allowed on the terrace.