In Washington DC, they hold an embassy open house every year where you can visit participating embassies free of admission. Seeing the insides are cool and it's great way to try a country's food, music, arts, etc. Some countries really use it as a time to sell their products or entice you to visit. Like when I went to Croatia years ago, they really wanted you to know that they filmed Game of Thrones there.
But it's also an opportunity to be fed a country's propaganda. I visited China's embassy this year and it was pretty normal for the most part but right at the end, they were handing out pamphlets about Muslims in China and a good about human rights from Chinese authors. When I went to Denmark a few years back, they had lots of stands and posters talking about how they are leading the fight in climate change so that was pretty cool. During a guided tour, they showed us a collage of Bill Clinton that they had in the embassy and they explained it was made by Denmark as a gift to him for helping to end the Bosnian War. They said he accepted it but then graciously said it would look good hanging on wall of their embassy lol