St. Olaf’s Church (Oleviste kirik) is believed to have been built in the 12th century and to have been the centre for old Tallinn's Scandinavian community prior to the conquest of Tallinn by Denmark in 1219. Its dedication relates to King Olaf II of Norway (a.k.a. Saint Olaf, 995-1030). The first known written records referring to the church date back to 1267, and it was extensively rebuilt during the 14th century.
A legend tells that the builder of the church, named Olaf, upon its completion, fell to his death from atop the tower. It is said that when his body hit the ground, a snake and a toad crawled out of his mouth. There is a wall-carving depicting this event in the adjoining Chapel of Our Lady.
Around 1500, the building reached a height of 159 meters. The motivation for building such an immensely tall steeple must have been to use it as a maritime signpost, which made the trading city of Tallinn visible from far out at sea. Between 1549 and 1625, when the spire burnt down after a lightning strike, it was the tallest building in the world. The steeple of St. Olav has been hit by lightning at least eight times, and the whole church has burned down three times throughout its known existence. Following several rebuildings, its overall height is now 123.7 meters.
From 1944 until 1991, the Soviet KGB used Oleviste's spire as a radio tower and surveillance point. It currently continues as an active Baptist church. The tower's viewing platform offers panoramic views over the old town and is open to the public from April through November.
The Kalozha church of Saints Boris and Gleb is the oldest extant structure in Hrodna. It is the only surviving monument of ancient Black Ruthenian architecture, distinguished from other Orthodox churches by prolific use of polychrome faceted stones of blue, green or red tint which could be arranged to form crosses or other figures on the wall.
The church is a cross-domed building supported by six circular pillars. The outside is articulated with projecting pilasters, which have rounded corners, as does the building itself. The ante-nave contains the choir loft, accessed by a narrow gradatory in the western wall. Two other stairs were discovered in the walls of the side apses; their purpose is not clear. The floor is lined with ceramic tiles forming decorative patterns. The interior was lined with innumerable built-in pitchers, which usually serve in Eastern Orthodox churches as resonators but in this case were scored to produce decorative effects. For this reason, the central nave has never been painted.
The church was built before 1183 and survived intact, depicted in the 1840s by Michał Kulesza, until 1853, when the south wall collapsed, due to its perilous location on the high bank of the Neman. During restoration works, some fragments of 12th-century frescoes were discovered in the apses. Remains of four other churches in the same style, decorated with pitchers and coloured stones instead of frescoes, were discovered in Hrodna and Vaŭkavysk. They all date back to the turn of the 13th century, as do remains of the first stone palace in the Old Hrodna Castle.
In 2004, the church was included in the Tentative List of UNESCO"s World Heritage Sites.