to catch the poor - infinitive
Catch is in the infinitive form because it is before to. An infinitive is when the main form of the verb is preceded by the word to. Similar to a main verb, it expresses an action.
covered with ancient artwork - participle
A participle phrase begins with a verb and often can include other modifiers. A participle is used as an adjective in the sentence. In this sentence, "covered with ancient artwork" is used to describe the walls.
A gerund is a verb that is used as a noun in a sentence. A gerund often ends in -ing. For example, Swimming is my favorite sport. In this sentence no one is actually doing the action of swimming. Swimming is a thing/sport in this sentence.