到了 + Place/Time, Subject + Verb Phrase
The phrase 到了 (dàole) means "upon arriving at" or "when one reaches" and is used at the beginning of a clause to set up a time or place condition. It indicates that once a certain point is reached, a follow-up action or situation occurs. For example, 到了那里 means "once you get there."
到了冬天,北方的河全都结冰了。
Dào le dōngtiān, běifāng de hé quán dōu jiébīng le.
When winter comes, all the rivers in the north freeze over.
到了机场才发现护照忘带了。
Dào le jīchǎng cái fāxiàn hùzhào wàng dài le.
It wasn't until arriving at the airport that I realized I forgot to bring my passport.
到了周末,这条街上到处都是人。
Dào le zhōumò, zhè tiáo jiē shàng dàochù dōu shì rén.
On weekends, this street is packed with people everywhere.