Translation:We will take you sightseeing to famous places.
Duo is a strange Birdie anyway. Just like all of you noticing so many glitches in this program, and we are all still waiting for a positive overhaul of it that will consider more correct translations than one only. Those working behind the bird should listen to all those wake-up calls and... Wake up and get to grabs with this issue ASAP.
For Duo's sentence, "a tour" or "tours" is a more natural fit.
"We will take you on a tour of famous places."
"We will take you on tours of famous places."
Also, the word 观光 is also a verb meaning "to tour."
"We will take you to tour famous places."
In English, "sightseeing" is typically used alone or with a specific (geographic) location and not a generalized noun (i.e. famous places). However, if the Chinese sentence was a bit different, the "sightseeing" construction could work more naturally.
"We will take you on a sightseeing tour of (all the) famous places."
I don't judge the Duo translators too harshly. Choosing the right words can even be difficult for native speakers when translating.
For a native Japanese, I could translate this sentence into Japanese quite easily.
I think it is a limit of Duolingo, as hq4 stated eight months ago. The current Duolingo style doesn't work between langauges highly apart. The construction of ideas differ significantly. No good translations dose not likely exist. Strict translations could become a big barrier to learn a language quite different from the base language. It would be better to stop to make translations at some point. Dive to the target language. I believe most Japanese do this to learn English.
This is a weakness of Duolingo (and traditional language classes) in general. Translation is never the best way to learn a new language. It's hard to imagine a different way for this app to do it, but the higher level modules at least should have more exercises that don't require translation: a question and answer in the target language for example, and instructions for what to do in the target language. Even the low level units can have match the picture with the word exercises. This is what (better) language schools do nowadays.
We will take you to famous places to go sightseeing?
I think in reality I would say "I know some famous places, let me take you sightseeing." This is the inherent problem with Duolingo. It stresses word-for-word translation. Translating word-for-word might be OK for Germanic and Romance languages, but it really doesn't work with Chinese.
These questions where we translate Chinese to English should therefore be pretty loose, and a broad range of English translations should be accepted.