Escape rooms are an established game genre that has become popular in educational contexts in recent years. Digital escape rooms are variations, which use digital environments and may be played by participants not present on site. Compared to physical escape rooms, digital escape rooms are characterised by lower implementation and application efforts and at the same time by reduced intensity of the experiences. There is little evidence to date as to whether these lowthreshold escape rooms are nevertheless sufficiently effective for learning. In this evaluation study, a learning activity based on a digital educational escape room (DEER) that uses the 360°-based spatial visualization (360VR) of a waterworks and a web-based form -- contributing guidance and the escape room-specific challenges -- is analysed. In the learning activity, students of environmental engineering study programs are asked to explore the 360VR-based waterworks guided by the instructions and challenges in the web-based form. Quantitative results of the study on learning outcomes and variables relevant to learning, such as emotion, motivation, and usability (N=73) are reported. The evaluation is supported by the qualitative results of guided interviews. Remarkably, some participants would have preferred to explore the 360VR environment without the guidance provided by the web-based form. Overall, the results show the learning effectiveness of the DEER, the efficacy of the web-based form as a guidance instrument, and values of learning-relevant variables that are conducive to learning. The DEER also achieved a high level of acceptance among students. Due to the low effort required for the creation of the DEER by lecturers and for application on the part of students, the presented combination of 360VR and web-based forms can be seen as a powerful low-threshold learning tool that enriches teaching.