What should a Muslim do if he finds a golden cross – a religious symbol – in a public street, whether he knows its owner or not?

A golden ornament with a cross or a religious symbol on it is treated like a found item (luqatah). The presence of the cross does not divest its owner of ownership. If the owner is known, it must be returned to him. If unknown, it should be publicized for a year. If its owner appears, it is given back to him; otherwise, one may benefit from it, provided the cross or religious symbol is changed or removed before using it.