Hmm... there were very few public toilets (= loos) in Portovenere and this underground one on the bottom of the picture was located at the end of the peninsula in front of a church. "Toilette a pagamento" means paid loo.
Btw do you call this very useful chamber a loo or a toilet?
Unique Suggestions: Use bar/restaurant loo.
Fun Alternatives: Don't drink much :-).
The centre of Portovenere is car free, I advice you to come early so you can park your car near the centre. The only parking spots are along the main road.