It is a typical technique of my region of origin, Liguria, and has been widely used in the architecture of the noble villas of Genoa since the year 1500 and derives from the best known, and most valuable, roman mosaic technique.

Step 1: What Is a Risseu

The rissêu is a path, square, churchyards or, more generally, a cobbled outdoor space; rissêu is in fact a term in the Genoese dialect to define the pebble.

The pebbles are chosen for their color and size (3-5 cm) on the beaches of the rivers or the sea or in the quarries. Pebbles of black color (serpentinite), white (quartz or calcite) or more rarely reddish (jasper). The laying work is painstaking and about 3 million pebbles are needed to make the square of a church.

Ancient laying technique

preparation of a coarse gravel sub-foundation;
"laying bed", usually formed by a layer of wet beaten sand added with a minimum part of lime;
dry substrate, about 6cm thick, consisting of river sand with the addition of natural hydraulic lime which is adequately compacted and leveled;
reporting a pre-established drawing that will provide a guide to the subsequent laying of the pebbles;
laying of pebbles;
leveling using a wood mallet;
at the end of the arrangement of the pebbles, a grouting is carried out with a very liquid hydraulic lime-based mortar until it clogs over the entire surface at the same time;
after about two hours, the excess mortar must be removed with the aid of a jet of water and a broom;
cleaning with water and sponges (or jute bags) to carry out the final polishing and highlight the heads of the stones with their chromatisms.

This technique is not seen very often nowadays because it takes a long time to make it and has very high labor costs; due to the low demand, there are few craftsmen left who still know how to make it to perfection. However, the available documentation is still abundant and therefore it is not a dead technique.

Step 2: My Design

In my garden there was already a risseu but, after more than a century from its realization, it was severely damaged by a tree roots and by the grass.
Therefore I decided to rebuild a new one, making it entirely by myself. The original drawing was lost and I made a new one with a floral theme; I recovered some images from which I took inspiration and inserted them into the CAD, with which I designed the decoration. I divided the length of the walkway into 6 rectangles made up of two alternating designs.

I decided to enclose the six rectangles inside a border made of solid brick, which replaces the classic jasper that I could not find from the local building materials dealer.
In addition, in one of the two designs, I have also included a LED underground light to illuminate the walkway at night.

Step 3: How I Did It

For my path I followed the modern technique, which includes:

a foundation made by reinforced concrete, about 10cm;
the subsequent drafting and compaction of a dry mixture of sand (70%) and cement (30%)
laying of pebbles;
leveling using a wood mallet;
at the end of the arrangement of the pebbles, a grouting is carried out with a very liquid concrete mortar until it clogs over the entire surface at the same time;
cleaning the top of the pebbles with the help of a wet brush and water.

The lime has therefore been replaced by cement, which allows greater durability and impact resistance. Furthermore, the reinforced concrete base offers greater safety with respect to the disintegrating action of tree roots and therefore there is less need for maintenance; every year it is necessary to clean with a jet of pressurized water to remove dirt.

The floral designs I have obtained from some white marble slabs that I have left over from the work in my house, using an angle grinder.
This choice of mine, which considerably lengthened the construction time, was necessary because my walkway is narrow (about 120cm) and if I had only used pebbles I would not have been able to use such a thin and detailed design but I would have had to fall back on something much simpler.

Final notes: it took me about 6 hours to build each of the six squares, excluding the time to cut the pieces of marble; the risseu can be driven over but it is better to use slightly larger stones (6-9cm)