On the southern shore of Petexbatún Lake lies Aguateca Cultural Monument, a small site. It was likely the final capital after Dos Pilas was taken over by Tikal. Few of the ruins have been excavated, but the trip here is an adventure. In Sayaxche you can arrange for a boat trip to the lake and ruins. There is a small visitor center at Aguateca, and guards at the site will allow you to camp here. Bring your own food and share with the guards. For an easier option, Martsam and other Flores tour operators can arrange a trip here, starting around US$150 per person. Remember, this in in an area used by drug cartels.
Aguateca, unknown, Guatemala