Rostov’s impressive Kremlin was built in the 17th century under the orders of the powerful Metropolitan Iona of Rostov. He wanted the town (which in those days still wielded some power in the region) to have one of the most beautiful Kremlins in the country and to that end he dug deep into the church's coffers to build this imposing fortress.
Nowadays within the Kremlin walls there are numerous museums, although unfortunately most of them are of little interest to foreign visitors. It is however well worth climbing up the Kremlin walls and the bell tower, taking a look in the cathedral and checking out the regular art exhibitions.
In front of the Kremlin is the huge 12th century Dormition of Mary Cathedral, which is in essence a working church - although it should be noted that inside it is undergoing a complete renovation. For a small extra fee you can also climb up the adjacent bell tower for a view over the surrounding area.
References:House of the Blackheads (Melngalvju nams) is a building situated in the old town of Riga. The original building was erected during the first third of the 14th century for the Brotherhood of Blackheads, a guild for unmarried German merchants in Riga. Major works were done in the years 1580 and 1886, adding most of the ornaments.
The structure was bombed to a ruin by the Germans June 28, 1941 and the remains demolished by the Soviets in 1948. The current reconstruction was erected from 1995 to 1999. Today the House of Blackheads serves as a museum and sometimes concert hall.