The river that Ljubljana has lived with for centuries brought it in the past both fortunes and misfortunes. Abundant rains often created floods as the river with a gentle incline would burst its banks. Towards the end of the 18th century, the Gruber Canal started to be dug out in order to redirect the water flowing in from the vast swampy plain to the south of the city. Consequently, the water volume in the river bed was reduced, although draining of the Moor continued until the early 20th century. At the beginning of the 20th century, the river and the canal were deepened and the embankments were strengthened following the plans of the engineer Ivan Podhagski. The Ljubljanica River was thus shifted away from the houses and deepened, the bridges grew higher, and the connection between the river and the city was interrupted. 

In 1913, the architect Alfred Keller from Graz made attempts to embellish the bleak reinforced concrete embankments. Yet, the outbreak of WW I slowed the works down, which ground to a halt in 1915. 

The work was only resumed in 1930 when attempts were made to ease the economic crisis by way of public construction works. The newly established provincial construction department assumed responsibility for managing the river bed and embankments. Thus, Plečnik was unexpectedly commissioned with the important task, which almost entirely let him have his own way with the planning. Namely, his work to date had earned him the complete trust of the director of the City Construction Office, the engineer Matko Prelovšek, and the conservator, Prof. France Stele. 

He initially embarked on renovating the banks of the Gradaščica River and continued by building the spacious 17-metre-wide Trnovo Bridge. It was conceived as a square on the water, embellished by birches planted in sunken planters along the bridge. 

The principal task was to widen the old Franciscan Bridge in the city centre. Plečnik kept the existing stone bridge which was flanked on each side by footbridges. All three of them were fitted with uniform balustrades. With the Triple Bridge and the tall poplars completing it, he created a triumphal arch at the entrance to the old quarter of the city.

Simultaneously, he was occupied with renovating the run-down foundations of the Cobblers’ Bridge. The bridges of Ljubljana have always been meeting points and market places, for which reason he designed the Cobblers' Bridge very much like the Trnovo Bridge, i.e. as a picturesque square on the water behind which the Castle Hill magnificently rises.

In 1932, he drew up plans for reconstructing the upper end of the Ljubljanica River. The stretch of the river between the Gruber Canal and the Prule Bridge has always been a popular bathing spot; accordingly, he had the banks reinforced with stones and weeping willows planted. He then reconstructed Trnovski pristan (Trnovo Quay) where the stone-clad terraces embracing the river bend descend to the water’s edge whilst the walking path is planted with weeping willows. 

Wherever possible, Plečnik built bridges so as to connect the medieval city at the foot of the Castle Hill with the well-arranged squares on the left bank, and to open views towards the river. To the side of the Philharmonic Hall building he constructed Gledališka stolba, a stairway leading down to the embankment, embellished with an elegant lamp post. At the same time, he also constructed the Gerber stairway having a river landing stage and a footbridge in his mind. 

Just before WW II, he produced designs for a roofed market alongside the Ljubljanica River. It formed part of a comprehensive construction project for the new Town Hall, which was never realised. On the right river bank he built a long colonnade running along the length of the roofed market. The architecture is in dialogue with the river as the walls facing it are pierced by a string of doors and windows. The pattern was broken by two loggias, and the space in the middle was intended for the unrealised Butchers' Bridge, which was to be the pinnacle of the composition. A café was planned on the opposite riverbank. 

Plečnik's last work involving the river was a sluice gate to control the water level. Next to it, he initially planned a landing stage and a small power station, yet in 1939 he completely changed his plan. The ornamentation features elements of Egyptian, Greek and Etruscan arts, indicating the significance of water in the lives of different civilisations and underscoring the memory of Ljubljana's classical past. 

Plečnik regarded the water element as a suitable complement to architecture. For him, the gradual arrangement of the city was a work of art in the making. By reconstructing the water axis and planting trees and other vegetation, Plečnik gave the city beside the Ljubljanica River a Mediterranean flavour. The urban area by the river created to suit the needs of townspeople is nowadays definitely the most pleasing section of the city.