The error in the sentence "We made it to the peek of Mt. Tamalpais!" is the word peek. The correct word instead of it would be peak since it refers to the top of the mountain.
The problem here is that both words, peek and peak are pronounced in the same way, however, they carry a complete different meaning that can change the complete sense of a sentence or result in a non-sense sentence.
Peek means a quick or furtive look as a noun or look quickly or furtively as a verb.
Answer: The mistake is the spelling of peek. It should be peak, which means the pointed top of a mountain as a noun and as a verb it means to reach a highest point.
