Perpetual lines is the proposal for the renewal of one of the most important squares in Pistoia. This town has got one of the most alive and busy historical city centre in Italy: lots of activities, both touristic and commercial, take place inside the ring of its ancient walls. During the week different open-air markets set themselves on the pedestrian streets and in many squares; this is a situation, a tradition that should go on, but without casting a shadow over historical and aggregative places. The aim of the Perpetual Lines project is to bring back Piazza dello Spirito Santo, one of these fascinating squares, to its original function: a common space, where people can go and admire historical monuments, take part to different kind of events (like concerts, open air cinema…) or just sharing their spare time. The research had begun from the study of the fluxes in this part of the city and the different accesses to the square. Then the design has been developed by fixing the statue of Niccolò Forteguerri as a cornerstone that defines the churchyard apart from the rest of the area, and choosing a paving that is contemporary and totally different from the bordering ones but that harmonizes with them. Another theme was to improve the comfort in the region adding vegetation and water to the project: the square then has been thought like a water mirror in which has been thrown a stone, producing propagation lines along which seats and trees replace slabs of paving. A real water mirror highlight the churchyard, playing also with the church facade reflections. Trees, pyrus calleryana chanticleer, are a deciduous species, therefore there is shadow during summer and the sun can warm up the site in winter. Lighting also plays an important role: all the seats has got a led stripe around them, and all the perimeter buildings facades are lighten by spotlights that underline their historical and artistic value. The plot in this way is well-lighted, so that it is safe also in the night, maintaining its romantic charme.