Former U.S. President Donald Trump is considering turning Alcatraz Island into a modern maximum-security federal prison, according to an Axios report citing people familiar with the discussions. The planning effort, still at an exploratory stage, envisions housing high-risk inmates on the San Francisco Bay landmark that currently operates as a national park and tourist site. Preliminary cost estimates range from about $1 billion for a scaled-back renovation of existing facilities to roughly $2 billion for a complete rebuild that would require razing remaining historical structures, Axios said. No formal proposal has been submitted to Congress or the National Park Service, which oversees the island, and financing details have not been made public.