Torre vs. torreón
The Spanish words torre and torreón both translate to tower, but they are not always interchangeable. The main difference lies in their specificity, size, and function, with torre being a general term and torreón referring to a specific type of large, defensive tower.
Torre
A2This is the general and most common word for tower. It refers to any tall structure that is higher than it is wide, whether it is modern or historical, such as a skyscraper, a bell tower, a control tower, or even a computer case or a chess piece (rook).
La Torre Eiffel es el monumento más famoso de París.
(The Eiffel Tower is the most famous monument in Paris.)
Desde la torre de control del aeropuerto se ve toda la pista.
(From the airport's control tower, you can see the entire runway.)
La princesa fue encerrada en la torre más alta del castillo.
(The princess was locked in the tallest tower of the castle.)
Mi ordenador nuevo tiene una torre con luces de colores.
(My new computer has a tower case with colored lights.)
En ajedrez, la torre se mueve en líneas rectas.
(In chess, the rook moves in straight lines.)
Cada domingo suenan las campanas de la torre de la iglesia.
(Every Sunday the bells of the church tower ring.)
Torreón
B1This word, derived from torre with the augmentative suffix -ón, refers specifically to a large, robust, and often cylindrical or polygonal tower. It typically has a historical and military connotation, as it was built for defense as part of a castle, fortress, or city wall. It is much less common in modern contexts.
El viejo torreón medieval vigilaba la entrada a la ciudad.
(The old medieval keep watched over the entrance to the city.)
Construyeron un torreón en cada esquina de la fortaleza para defenderla.
(They built a large defensive tower on each corner of the fortress to defend it.)
El torreón del castillo resistió el ataque de los cañones.
(The castle's great tower (or keep) resisted the cannon attack.)
Desde lo alto del torreón, los soldados podían ver al enemigo acercarse.
(From the top of the large turret, the soldiers could see the enemy approaching.)
La ciudad de Torreón, en México, debe su nombre a una estructura defensiva de este tipo.
(The city of Torreón, in Mexico, owes its name to a defensive structure of this type.)
Los arqueólogos descubrieron los cimientos de un antiguo torreón romano.
(The archeologists discovered the foundations of an ancient Roman defensive tower.)
Summary
In summary, use torre as the default, all-purpose word for any kind of tower. Use torreón only when referring to a large, sturdy, historical tower built for defensive purposes, like those found in old castles or fortresses. A torreón is a specific, more robust type of torre.