Foundation of Yaroslavl
According to legend, Yaroslav was traveling along the Volga from Novgorod to Rostov when he was attacked by a bear during one of his stops. He and his retinue managed to kill the bear with an ax. After this, the prince ordered a small wooden fortress to be built on an impregnable cape above the Volga, which was named Yaroslavl after him.[1]wikipedia

Caption: “At this place in 1010 Yaroslav the Wise founded Yaroslavl”
1030 – foundation of Yuryev (Tartu, Dorpat)
«In the summer of 6538. Yaroslav has been going to the Chuds for seven years and he won, and he built the city of Yuryev.» – Tale of Bygone Years
This is one of the most reliable and earliest written records of the relationship between the Baltic peoples and the Kievan princes. Presumably, Yaroslav’s campaign was prompted by the fact that the Estonians took the side of Canute, the King of Denmark and England, whose opponent Olaf the Stout, the King of Norway, received help from Yaroslav.
The fortress founded by Yaroslav was located on the highest elevation of a swampy floodplain of the Emajõgi River. This was where trade routes connecting the southern Estonian and Latvian regions, as well as the craft centers of Novgorod and Pskov with the ports of Northern Estonia and the Baltic Sea, intersected.[2]sedmitza.ru
After Yaroslav the Wise died, the city was burned down by local tribes in 1061, but it was rebuilt time and time again.
Tartu is one of the oldest cities in the Baltic region. The permanent settlement of humans on Toomemägi Hill dates back to the 5th century, and the stronghold dates back to the 6th-8th centuries. It was called Tarbatu (tarvas means “aurochs” in Estonian). Hence the later Estonian name Tartu, as well as Dörpt, Dorpat, or Derpt. Today, Tartu is the second most populous city in Estonia after Tallinn, and the center of the county.
1032 – fortress cities of the Porosskaya line
In the year 6539 (1031), Yaroslav and Mstislav, having gathered many warriors, went to fight against the Poles. They again took control of the Cherven cities and waged war on the land of Poland, bringing back many Poles and dividing them among themselves. Yaroslav settled his Poles along the Ros River, where they still live to this day. – the Radzivilov Chronicle.
The Porosskaya defensive line — was a chain of watchtowers along the Ros River, established during the era of Ancient Rus to protect against raids by nomadic steppe tribes.
Belaya Tserkov (Yuryev-Russkyi)
The city was a constant thorn in the side of the nomads, continually obstructing their campaigns to the north. It was destroyed to its foundations several times. The last time Yuryev was devastated by nomads was in the 13th century, and it was rebuilt with a new name – Belaya Tserkov.[3]Wikipedia
Korsun
In 1240, the city was destroyed by Batu Khan, and three centuries later, it became one of the centers of the uprising of Bohdan Khmelnytsky.
The modern name of the city was given in 1944 in honor of Taras Shevchenko, who was born 34 km from Korsun in the village of Morintsy. It is now a district center in Ukraine.[4]wikipedia
Boguslav
The first mention of the settlement as a fortress to protect against Polovtsians dates back to 1195. However, there is a legend that Boguslav was founded in 1032 by Kyiv Prince Yaroslav the Wise.
After defeating the nomad troops, the prince climbed one of the hills where a small settlement was located. Surrounded by his warriors, who greeted their prince with the words “Glory to Yaroslav!” (old.rus – “Slava Yaroslavy”) – He, wiping the sweat from his forehead, looking after the enemies who fled, wearily said: “Glory to God!” (old.rus – “Slava Bogu”) These words were echoed by many voices: “Glory to God!” From that time on, the fortified settlement became known as Boguslav, and later a city.[5]beket.com.ua
Other cities
The following cities were also founded during the reign of Yaroslav the Wise: