This glorious castle is located in the city of Kuressaare (former Kingisepp), that on the island of Saaremaa (aka Ezel), in the country of Estonia. Look at the map - you'll understand everything without words ...
It is more conveniently to get there from the capital city of Tallinn to Virtsu settlement. From Tallinn to Kuressaare is about 220 km (4.5 hours by bus), although in the summer in the last week of June it can be much longer travel, because of "Ivanov's Nights" and all Estonians traditionally break to Saaremaa, this is the custom. The ferry from Virtsu to Saaremaa goes every 20-25 minutes. There is a buffet on the ferry - pies, beer, water, etc.
PS: In Kuressaare the airfield is and it seems like every day there are Avies flights from the city of Tallinn. At a price - one and a half times more expensive than a bus.