Despite numerous investigations and theoretical models, tafoni weathering is still not fully understood largely because of limited data available on temperature, moisture and salt regimes. We investigated tafoni developed in granite in the Tafraoute region, Morocco, through an exploratory, two-week multi-method field campaign. Temperatures were measured with iButtons and by means of infrared thermography; moisture distribution and progress were captured with handheld moisture sensors and with drilled-in iButtons. Salts were analysed in drill dust samples from different positions and rock depths.The results derived from very different techniques mutually support one another. Salts and moisture are concentrated near the base of the investigated tafoni, probably due to a saturated pore water body around the base of rock tors. Salts are accumulated close to the rock surface in tafoni, but not on the surrounding rock surfaces. A clear correlation was found between moisture and salt contents. Within a tafone, areas of higher humidity also display increased salt concentration near the surface. The temperature/humidity records allied with ionic analyses suggest that sodium sulfate dominates and is likely to undergo frequent phase changes from thenardite to mirabilite and vice versa. Two pathways of salt transport in and around tafoni are assumed based on the data: infiltration with rainfall on the top and around tors and boulders, and capillary rise from saturated pore water bodies to the surface.

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<p>Moisture and salts cause considerable damage to built and rock-hewn heritage. Rock moisture is a key factor for numerous decay processes, but there is limited knowledge of salt and moisture distribution because measurements of spatial and temporal moisture distribution still remain challenging. The medieval cave town of Uplistsikhe (Georgia) is hewn out of very soft Lower Miocene sandstone and is a typical example of a heritage site suffering from progressive decay. We present data on moisture and salt distribution derived from a multi-method approach, including microwave sensor monitoring (MW-mon; continuously over 2 yrs), microwave handheld sensors (MW), 2D-resistivity profiles (ERT), rock sampling by drilling, and salt extraction by paper pulp poultices (PPP).</p> <p>Microwave monitoring was applied for the first time (to our knowledge) in a long-term monitoring of heritage sites. We used equipment from hf-sensor (Germany) with two types of microwave reflectivity sensors penetrating approx. 7 cm and 13 cm deep, respectively. The sensors were installed inside and outside of two prominent caves (Grand Hall and Long Hall). MW, ERT, PPP and drilling were carried out in four caves (the two mentioned plus Blackberry Hall and Teatron). Careful laboratory calibration using samples from the site was necessary to produce quantitative results for MW-mon, MW and ERT.  </p> <p>MW-mon showed pronounced annual fluctuation with highest moisture saturation occurring in summer. The moisture maximum in the caves lags 2 months behind the spring precipitation maximum and might be partly caused by air humidity condensation amplified by salts. Heavy rainfall events cause additional moisture pulses by seeping through the rock or by capillary rise. Spatial moisture distribution derived from MW shows relatively dry rock outside the caves and different patterns of moisture ingress into the caves: Capillary rise from the base, ingress through fractured or otherwise water-permeable areas of the roofs or back walls. The spatial patterns are confirmed by ERT; however, calculated moisture saturation differs between MW and ERT due to electrical conductivity effects of salty pore water.</p> <p>All drill samples from the caves are significantly saltier on the respective surfaces, which points to the rate of evaporation being smaller than the outward migration of salts. Outside the caves, flaking of thicker layers (several cm) point to deeper layers of salt concentration caused by higher evaporation from the surface; flaking at the "lips" above the caves is probably also amplified by stronger temperature and moisture fluctuations. The main ions everywhere are  Ca<sup>2+</sup> and SO<sub>4</sub><sup>2-</sup> (subordinate K<sup>+</sup>) while at the strongly flaking surfaces of Grand Hall, Na<sup>+</sup>, Cl<sup>-</sup> and NO<sub>3</sub><sup>2-</sup> are also present. Summing up, the results show very diverse and complex patterns of moisture and salt distribution at an apparently homogeneous site.</p>

<p>A variety of weathering processes is controlled by moisture movements in porous rock. However, the quantitative assessment of small-scale moisture levels and fluctuations in-situ, over longer time periods, is still a challenge. The aim of our investigation is to close this gap with a microwave-based moisture monitoring system, installed at the cave town Uplistsikhe in Georgia, which oldest structures date back to the early Iron Age (10<sup>th</sup>-9<sup>th</sup> centuries BC).</p><p>Two morphologically different cave structures were equipped with two pairs of sensors, each covering two depth ranges, at two positions to detect different moisture contents and sources. These are considered the main driver of the highly accelerated weathering processes and decay of Uplistsikhe.</p><p>With the long moisture monitoring dataset of 12 months, combined with meteorological data from the study site, seasonal moisture variations and environmental-rock interactions are detected. Preliminary data from the first eight months of monitoring is presented.</p>