The BT Tower, a futuristic landmark on the London skyline for 60 years, is to become a hotel, owner BT Group PLC said Wednesday. The company, formerly known as British Telecom, said it has agreed to sell the tower to U.S. company MCR Hotels for 275 million pounds (about $347 million). The 581-foot (177-meter) structure, originally called the Post Office Tower, was completed in 1964 and was London’s tallest building until 1980.