## 1 Introduction  
Techniques that incorporate digital content into the physical world are now numerous. In 1994, [PERSON] and [PERSON] introduced the notion of a _virtuality continuum_ among these methodologies, offering access to a virtual reality, a completely simulated virtual scenario digitally created, and actual reality, the physical world in which we live. Mixed reality (MR) procedures are typically positioned in the middle of such a continuum, merging both virtual and real contexts. In mixed reality approaches, physical and 3D digital objects coexist and interact in real-time [1]. Mixed reality superimposes and aligns virtual and real settings, rendering graphical information onto tangible items. It also anchors virtual objects onto the physical context, giving the user the possibility to acquire a high degree of interaction and collaboration with such a hybrid environment [2]. Advancements in input systems, display technologies, digital vision and graphical-processing enhancement have fostered the development of mixed reality in cultural heritage and archaeology. Indoor and outdoor mixed reality, augmented reality (AR) and virtual reality (VR) applications [3] have been created for educational [4; 5] and exhibition purposes [6; 7], virtual museums [6; 8], reconstructing lost or intact archaeological sites [9] and manipulating, displaying and exploring in situ features [10] (see Figure 1). The markerless mixed reality approach refers to applications that depend on the natural features of a surrounding rather than the fiducial identifying images, which are markers containing visual hallmarks, to overlay virtual 3D objects into a real setting [11]. Currently, markerless mixed reality explorative/reconstructive applications account for less than 1.5% of the total _virtuality continuum_ software programmes used in cultural heritage and archaeology [3]. The vast majority of this 1.5% consists of cultural heritage projects, and only a small portion are archaeological applications [12; 13]. Furthermore, from this fraction, a limited number of projects deal directly with the field of excavation. There are some pioneering examples among them [14; 15; 16], as well as some more recent approaches [17; 18; 19; 20; 21]. These works often offer tridimensional reconstructions of a site (e.g., structures, buildings, walls, gardens, etc.) by using mixed reality. Very few projects propose MR approaches that enable the archaeologist to see the finds as they were discovered and in correspondence with the features still present at the excavation. Here, we aim at facilitating access to an innovative application for reconstructing and exploring previously excavated sites by providing archaeologists with a device that directly interacts in situ with both virtual (formerly extracted) and real finds. From this perspective, the current approach contributes to what is called _virtual heritage_, i.e., the utilisation of computer-based interactive technologies to register, preserve or recreate artefacts and sites of cultural value [22]. Figure 1: Venn diagram showing the percentage of implementations for distinct purposes used in cultural heritage and archaeology, based on the use of a single shared technology (e.g., markerless mixed reality, representing 1.5% of the total applications. Part of it overlaps both exploration and reconstruction purpose areas), after [3]. When visiting a formerly unearthed archaeological area, it is hard to mentally conceive or reconstruct the precise location of every discovered find. Few elements physically persist after the extractive operations. A previously excavated site often maintains only the bedrock, natural terrain and maybe some sections. Likewise, when returning to a formerly unearthed area for taking samples of a preserved section, it frequently necessitates a long series of measurements with a total station to identify where features close to that section were before the extraction. Even then, researchers cannot directly experience or envision previously excavated finds in a 3D space.