scaled down, the project is still the second biggest private real estate venture under construction in New York City. The agreed-upon plan would expand Riverside Park by and extend Riverside Drive to the south as Riverside Boulevard.. The new Riverside Park South, stretching between 72nd and 59th streets, is the central element of the development. Portions of the former rail yard, such as the New York Central Railroad 69th Street Transfer Bridge, are incorporated into the new park. Route Starting at 72nd Street, Riverside Drive passes through the Manhattan neighborhoods of the Upper West Side, Morningside Heights, over Manhattanville in West Harlem by way of the Riverside Drive Viaduct and through Washington Heights. Below 72nd Street, Riverside Drive continues as Riverside Boulevard which stretches through Riverside South to 59th Street where it merges into the West Side Highway. Only a few stretches of Riverside Drive were built along an older road; due to the hilly terrain, Riverside Drive crosses a natural cleft in the bedrock at 87th Street on an iron viaduct and passes over 96th Street, Tiemann Place and 135th Street, and 158th Street on further viaducts. At Tiemann Place and 135th Street, and at 158th Street, an old alignment is present, also named Riverside Drive, while the viaduct portion or main route is officially named and signed "Riverside Drive West". The viaduct between Tiemann Place and 135th Street is called the "Riverside Drive Viaduct", as it is the most notable of the Riverside Drive viaducts. At its north end, Riverside Drive merges with the northbound lanes of the Henry Hudson Parkway; when the parkway was built, the Henry Hudson's northbound lanes used the roadway of Riverside Drive. In 2005, the retaining wall of Castle Village collapsed onto both Riverside Drive and the northbound lanes of the Henry Hudson Parkway. The wall was repaired and the roadway reopened in March 2008. Riverside Drive terminated at Grant's Tomb in a cul-de-sac, prior to the construction of the Manhattan Valley viaduct, spanning 125th Street, completed in 1900. North of 158th Street the right of way which currently carries the name Riverside Drive was known as Boulevard Lafayette, which led to Plaza Lafayette in Hudson Heights. The section exiting the parkway at the Dyckman Street exit and ending at Broadway is still known as Riverside Drive. The New York City Bus route serves Riverside Drive from 72nd to 135th Streets. The and