Translation of review in Spanish

I hope you can understand the corrections this way... Two small errors. let me know if there is a word or sentence or phrase that you didn't understand! I will try to think more on the "since" question...
It must have taken them years and ten's of thousands of workers to accomplish the tasks of constructing such spectacular compounds. We took many pictures and walked back to the taxi.
If we had more time, we would have stayed overnight in Aguas Calientes and visited Machu Picchu before 10 a.m. when the crowd (from Cusco) arrives.