Sleepy and slatternly, SAN CARLOS has to be one of the most unprepossessing towns in the whole country. An air of lassitude, if not downright stasis, pervades its ramshackle buildings and muddy streets. This could, of course be the fault of the fire which destroyed most of the town in 1984, or the climate of heat and torrential rain, but there appears to be a general lack of civic pride or willingness to treat the place to a splash of paint. Travellers come through San Carlos from Los Chiles in Costa Rica in order to make the lake trip to Granada, or to go to Solentiname. Increasingly, more determined ecotourists are coming through to pick up a boat to the El Castillo and points further along the Río San Juan.