Masaya Volcano is an interesting site. We have driven up close to the rim and then follow the stairs to the top for an bird eye view. Masaya continually emits large amounts of sulfur dioxide gas, coming from the active Santiago crater, that might bother your breathe. Stay within the pathway and don't venture to close to the rim.
One interesting story that I've learned from a local is that when Spaniards came to this area and approached the mouth of the volcano, they were sure that gold is is there to be be taken. So they rappeled down into the crater with buckets to collect the incandescent gold, which was just pure lava....Most of them haven't got the chance to return.