level rise in the entire world. According to some estimates, hundreds of thousands of people in its low-lying areas may already have to be relocated before 2030. The 2022 IPCC Sixth Assessment Report estimates that by 2050, Alexandria and 11 other major African cities (Abidjan, Algiers, Cape Town, Casablanca, Dakar, Dar es Salaam, Durban, Lagos, Lomé, Luanda and Maputo) would collectively sustain cumulative damages of US$65 billion for the "moderate" climate change scenario RCP 4.5 and US$86.5 billion for the high-emission scenario RCP 8.5, while RCP 8.5 combined with the hypothetical impact from marine ice sheet instability at high levels of warming would involve up to US$137.5 billion in damages. Additional accounting for the "low-probability, high-damage events" may increase aggregate risks to US$187 billion for the "moderate" RCP4.5, US$206 billion for RCP8.5 and US$397 billion under the high-end ice sheet instability scenario. In every single estimate, Alexandria alone bears around half of these costs. Since sea level rise would continue for about 10,000 years under every scenario of climate change, future costs of sea level rise would only increase, especially without adaptation measures. Cityscape Due to the constant presence of war in Alexandria in ancient times, very little of the ancient city has survived into the present day. Much of the royal and civic quarters sank beneath the harbour and the rest has been built over in modern times. Pompey's Pillar "Pompey's Pillar", a Roman triumphal column, is one of the best-known ancient monuments still standing in Alexandria today. It is located on Alexandria's ancient acropolis—a modest hill located adjacent to the city's Arab cemetery—and was originally part of a temple colonnade. Including its pedestal, it is 30 m (99 ft) high; the shaft is of polished red granite, in diameter at the base, tapering to at the top. The shaft is high, and made out of a single piece of granite. Its volume is and weight approximately 396 tons. Pompey's Pillar may have been erected using the same methods that were used to erect the ancient obelisks. The Romans had cranes but they were not strong enough to lift something this heavy. Roger Hopkins and Mark Lehrner conducted several obelisk erecting experiments including a successful attempt to erect a 25-ton obelisk in 1999. This followed two experiments to erect smaller obelisks and two failed attempts to erect a 25-ton obelisk. The structure was plundered and demolished in the 4th