Machu Pichu could have been discovered countries ago, but it was not found until 1911.
1.This is an example of a compound sentence
2.This is an example of a simple sentence
3.This is an example of a complex sentence 4.This is an example of a compound-complex sentence
The example is far more detailed than a compound and simple sentence because it provides more than 1 fact and the sentence is conjoined by a comma which makes it a compound-complex sentence.