El Castillo de la Imaculata Concepcion, located on the San Juan river of Nicaragua, was built in the 1670's to protect Lake Nicaragua and its ports, mainly Granada and Leon. Construction began shortly after an attempt was made by the pirate Gallardito to take control of the port of Granada and all the profits gained by its trade industry.
You can get in from San Carlos at the south-east corner of the Lago Nicaragua by boat (Cordobas $75 pp = $4 US).
Boats leave San Carlos at 6:30 am, 8 am, 10:30 (high season), 12:30, 2:30, 4:30
Reading a book in the library which is right inside the castillo. Listen to the sounds of the village and the water running down the river while reading Edouardo Galleanos book Las Venas abiertas de Latinoamerica.
Nena Lodge, Main Street (East end). Lovely place in the east end of town not far from Hotel Victoria. This place is basic but clean and the staff are lovely. Rooms have mosquito nets and fans. They also run tours which are potentially much cheaper than if you go through the tourist office by the dock (Nena was $72 for a 5 hour trek for up to 4 people, $18 each assuming you can rope in others, which is half the charge elsewhere). Ask for Orlando as your guide - he was exceptional. $10 dbl.