Most ancient structures that are still standing have very thick walls made of rock or earth. A lot of existing gravity dams will be around for thousands of years even if civilization collapses because the construction is similar.
Most modern skyscrapers and large buildings will be around for as long as we deem them useful, I could envision the empire state building lasting 1000+ years as long as society continues to maintain it.
Most ancient structures that are still standing have very thick walls made of rock or earth. A lot of existing gravity dams will be around for thousands of years even if civilization collapses because the construction is similar.
Most modern skyscrapers and large buildings will be around for as long as we deem them useful, I could envision the empire state building lasting 1000+ years as long as society continues to maintain it.