Use of 了 - when is it necessary? 我走到海滩边，看到一幢房子前有一块写着“旅馆”的牌子.
I went to the seaside and saw a building with sign in front of it which said 'hotel'.

Authentic Chinese with my translation. This is in the past. But there is no 了. Is this a bit like the English historical present? Or is there an explanation to do with aspect? Is my translation using the past a mistranslation?
Tense in Chinese is inferred from context, there are no grammatical constructs for it.

了 indicates completion, not past time per se.