This keynote paper describes piling typology, i.e. Aids to navigation, Mooring and berthing and Pileworks. Furthermore, it describes damages to pilings and public tests on alternative materials and protection. Final remarks: Today, all the pole types admitted by the Memorandum of Understanding can be seen in the lagoon. Plastic poles are common for the mooring of small boats and as stilts in some stilt structures in the City of Venice, whereas the majority of the large waterway markers are still in wood, almost always oak, both protected and unprotected. Environmental compatibility implies the evaluation of "parameters" which act at hierarchically different levels. The ecotoxicity and durability, evaluated in the tests, are applicable to two different aspects of environmental compatibility. Ecotoxicological assessment and risk analysis must represent the main criteria for the admissibility of a material as they regard the health of the organisms and, consequently, direct threats to the ecosystem. The durability of a material or a manufact, has reflections on economic sustainability, on ecological footprint, on waste management and on navigation safety. Landscape, historical, aesthetic and social evaluations complement the ecosystem in the definition of environment. All these aspects are very important in socio-ecologically sensitive environments such as Venice and its lagoon and must be supported by clear criteria for the choice of admissible materials and the design of structures. Life cycle assessment is necessary starting from the sustainability of the sources to the final destination. It is not sustainable the sacrifice of a hundred-year-old oak for a life service of few years. For the allowed plastics the possibility of a complete recycling of materials and an investigation on the release and fate of micro and nano plastics are necessary. To the moment it seems that the oak piles, duly protected by filling with iron staples or iron mesh, are the best compromise between durability, economy, environmental health and safety. On the other hand, oak wood is valuable and it would be a great advantage if it could be replaced by softwoods, very abundant in the Alps, fast growing and much cheaper.

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