Caja de Muertos (literally "The box of the dead") is the highest point of Isla de Muertos a.k.a. Coffin Island, off the Southern (Carribean Sea) shore of Puerto Rico. Of course the place got its name from its very distinctive shape.
The dry tropics' thorny vegetation of the island pretty much prevents any off-trail hiking. Luckily, the top of the island used to have a working lighthouse for over a century, until the hurricanes and difficulties maintaining it on this uninhabited island have finally forced its closure. The former lighthouse service trail to the top is described below.
Caja de Muertos is a small mountain as you've already guessed, and you can imagine a certain wink in my eye now that I am creating this page. But I promise no deluge of beach pictures :).
The regular ferry service to Caja de Muertes is from Ponce harbor, on weekends and holidays only all day long. Follow Carreteria 14 South to the Port Zone. Once the divided road pulls between the port warehouses, look for the brown sign pointin left to La Guancha / ferry on the median strip.
On weekdays, one would need to charter a boat - there is no shortage of snorkeling operators serving a wonderful reef on the NE end of Isla de Muertos.
El Faro trail
The summit trail (first left turn from the pier) is well visible on the topozone map and has some interpretive signs. It crosses the thicket of acacia and tall cacti, then follows the right fork uphill, not far from a stone monument at the former secret gathering place of local Masons, and finally circles the mountaintop lighthouse in a loop.