Luke P.
Google
A former castle and royal residence that dates back to the medieval times, Toompea Castle now functions as the central location for the Estonian government, where the parliament sits.
The place is usually closed to public visits as it's a government building, but occasionally holds public tours (either twice or once per week). We were lucky to be able to join a tour in August on a Thursday, when the parliament was not in session, where we were given a thorough briefing of Estonian history and caught a glimpse of the different sections of the building.
You can learn more about the public tours through the website, no sign ups required, they just need a photo ID from you with a security check. Really enjoyed the behind the scene tour into the building and its inner workings. Even without the tour, it's worth just dropping by the area to just admire the function of the place and its rich history.