The three-nave Romanesque nave with the two towers was built around 1100. Around 1200, the towers were given late Romanesque gables. The Gothic period brought a new choir around 1350, which stands on the stump of a Roman city wall tower. Around 1467, the building was extended between the towers. After French Revolutionary troops occupied Koblenz in 1794, St. Florin was secularised in 1803 and used as a magazine. At Napoleon's instigation, the church was even to be converted into a municipal slaughterhouse with stalls in 1807. But this did not happen, as the Prussians took over the regiment in Koblenz in 1815 and King Frederick William III transferred the building to the Protestant military and civil congregation in 1818. It was consecrated as a Protestant parish church in 1820, making it the first Protestant church building in Koblenz. In 1899, the towers received their pointed spires. The interior of the nave is harmonious and clearly proportioned. Baroque putti in the corners remind us that the vaulting, which was only added in the 16th century, was restored in 1708 after the destruction of 1688. A cannonball is stuck in the vault above the baptismal font. It was inserted here when the vault was repaired to commemorate the destruction of the city.