Translation:The Parliament lies next to the river.
This is a tricky one, I admit, in English, in that we can use the same base noun for both a structure and an organization. Adding the article "the" is the only way we use to differentiate the two. Capitalizing "Parliament" won't help in spoken English, so we have historically used "the" to allow us to differentiate. While Hungarian might use "A", to refer to the building, in English we would.
I don't perfectly understand. So 'the parliament' means the system/organization or the building?
Anyway, we use Parliament in Hungarian only in the case of the building. The organization is 'országgyűlés' (' country assembly' literally) or in a more complex way: 'parlamentáris rendszer' -'parliamentary system'.
No, not only in American English!
"A capitol is a building in which the legislative body of government meets." - in all English dialects - see: https://www.grammarly.com/blog/capital-vs-capitol/