古老(gǔ lǎo) - ancient, age-old in Mandarin

古老 (gǔ lǎo) describes something that has been around for a very long time: a city, a building, a tree, a custom, a legend, a language. It carries a note of respect. Calling a tradition 古老 says it has weight, not that it is out of date.

Note the tone sandhi. Two third tones in a row means the first is said as a second tone, so 古老 comes out as gú lǎo in speech even though it is written gǔ lǎo. That rule catches a lot of learners on this particular word.

The English-speaker trap is using it for people. 古老 never means an old person; that is 老 on its own, or politely 年纪大. Nor does it mean stale or outdated, which is 过时. Keep 古老 for things whose age is the point of them.