北京正在进行的全国文物“四普”，有哪些重磅新发现？

Group 1 - The Beijing government is actively conducting the fourth national cultural relics census, which started in November 2023, with a focus on collaboration between city and district levels [1] - The census has led to significant discoveries in the Yanqing District, including nearly a hundred new relics related to the Great Wall, such as beacon towers and brick kilns [2][4] - In the Changping District, the census has identified 145 new relic clues, including the rare Liao-Jin period water conservation site, which fills a gap in historical water management infrastructure [4][5] Group 2 - The Changping District has completed the second phase of field investigations and is now in the data review and relic identification phase, with plans for publicizing results and initiating protective measures for significant finds [5] - The discovery of a suspected Han dynasty boundary stone in the Mentougou District may redefine the known history of rock carvings in Beijing, dating back at least 1800 years [7][8] - The Huairou District has employed photogrammetry technology for a comprehensive 3D scan of the Great Wall, enhancing data collection for the fourth cultural relics census [9]