He /spoke of/ war and peace and many other topics that day. The topic /of which he spoke/ was complex. The verb here that means to speak about a topic is /to speak/of a topic/: to mention
The party /at which/ he spoke/ was noisy. Phrase: A party is held /at a place/. It is implied.
The situation /in which/ we found ourselves was dire. Phrase: /to find oneself /in a situation.
The bonds /from which/ we broke free were tight. phrase: to /break free/ frombonds.
The town /to which/we were driving was 50 ks away. phrase: to /drive/ to a place.