Why anyone would want to leave this gorgeous Carnegie Hill penthouse at 1150 5th Avenue will remain a mystery for the ages. For some reason, the penthouse’s former owners, Karim Rashid and Tracy Buescher, have decided to sell their beautiful 5th Avenue pad. However, someone just hit the jackpot when they scooped up the 3BR/3.5BA beauty, built in 1924 by J.E.R. Carpenter – the unsung hero of 5th Avenue. The co-op was designed by architect Charles Platt, the award winning designer responsible for Washington D.C’s Freer Gallery of Art.