Callejón vs. callejuela
The Spanish language has a rich vocabulary and some words, though seeming similar in meaning, may have subtle differences in usage. In this case, we are considering the words 'callejón' and 'callejuela', which both generally refer to an alley or narrow street.
Callejón
'Callejón' typically refers to a narrow, often pedestrian street that is enclosed between close buildings. It gives a sense of being narrower and longer.
El gato se escondió en el callejón.
(The cat hid in the alley.)
El callejón sin salida resultó ser un atajo.
(The dead-end alley turned out to be a shortcut.)
Callejuela
'Callejuela' also refers to a small or narrow street, but it isn't necessarily enclosed tightly by buildings as with 'callejón'. The term connotes a sense of quaintness or charm, often used when describing picturesque streets in older townships.
La casa estaba ubicada en una bonita callejuela del casco antiguo.
(The house was located in a nice little street in the old town.)
Me perdí en las callejuelas de la ciudad vieja.
(I got lost in the alleyways of the old city.)
Summary
While 'callejón' and 'callejuela' both indicate small, narrow streets, 'callejón' gives an impression of a more narrow passageway typically sandwiched between taller buildings and can imply length. On the other hand',callejuela', while also indicating a small street, suggests a more charming or rustic locale typically found in older neighbourhoods.