By 9 AM, there was already a long line at the entrance. Fortunately, we were part of a skip-the-line tour, allowing us direct entry and saving us a lot of time. Descending into the Basilica Cistern was truly breathtaking; I never imagined such a massive underground reservoir, built 1,500 years ago, could be so well-preserved to this day. After the guide finished explaining, we were free to explore at our leisure, with no time limit, allowing us to meticulously admire every column, every corridor, every detail. This experience was fantastic, and I highly recommend it; everyone visiting Istanbul should come and see this.