The county seat lies on the Warta river in the Koło Basin, about 30 km east of Konin. Its location has made it an important road junction linking western Europe with Warsaw and Moscow.
The town was located by King Casimir III the Great (1333–1370) in 1362 and was a royal estate and the seat of the starosta. The name (“koło” means circle, ring, wheel etc. in Polish) probably derives from the fact that the settlement was established on a river bend. This also lent it a defensive character.
Up until the 17th century, the town grew on account of its attractive location, trade and handicrafts expanded, and the aristocracy assembled in the regional councils of Wielkopolska province. The Swedish Invasion (1655–1660) brought about the decline of the town, which only began to recover from having been burnt down during the war in the 19th century as a result of building factories.
The town was transferred to the Prussian Partition following the Second Partition of Poland in 1793. It was soon returned to Poland after the Kościuszko Uprising of 1794 – when it was governed by the insurgents – and then the Duchy of Warsaw (1807–1815). Following the Congress of Vienna, Koło was made part of the Kingdom of Poland (1815–1918), informally known as Congress Poland.
Koło was liberated from Nazi occupation (1939-1945) by the Soviet 1st Belorussian Front on 20 January 1945. Today, the town is a major industrial centre and a centre for education and tourism.
The ruins of a medieval castle dating from the 2nd half of the 14th century can be found about 2.5 km north-east of the town centre.
The Church of the Raising of the Holy Cross, built at the turn of the 14th and 15th centuries is south of the marketplace. A Gothic pulpit and the stone tomb of Jan of Garbów, son of that famous knight and paragon of chivalrous virtue, Zawisza, the Black Knight, is inside.
Also of interest to tourists is the 18th-century Church of the Visitation and Bernardine monastery built on the site of a medieval complex destroyed by river flooding.
Next to the historic railway station, built during the 20 years between the wars, stands a boulder dedicated to the memory of the 80,000 Jews transported here from the Łódź ghetto to the Chełmno extermination camp in Chełmno nad Nerem.