Learn Portuguese (Portugal): Tudo estava tão escuro que não víamos nada sob o teto da caverna. - Everything was so dark that we couldn't see anything under the ceiling of the cave.

Both prepositions translate to under. In European Portuguese, debaixo de is more common in everyday speech for physical locations, while sob is slightly more formal or literary. However, sob is perfectly natural for physical spaces like this cave ceiling. Keep in mind that for abstract concepts, such as being under pressure, you must exclusively use sob.

Why are the verbs in the Imperfect tense (estava, víamos) rather than the Preterite?

The sentence describes a continuous background condition (the darkness) and an ongoing state during that time (the inability to see). The Imperfect is the correct tense to set the scene and describe ongoing past conditions, whereas the Preterite would imply a single, completed event.

Why is there a double negative in não víamos nada?

In Portuguese, if a negative word like nada comes after the verb, you must put não before the verb. It translates literally to we did not see nothing, but it is the standard, grammatically correct way to say we did not see anything.

Can I use muito instead of tão in the phrase tão escuro que?