I first saw this building from The High Line, the elevated garden in the Meat-Packing district of Manhattan, and felt an immediate attraction. Turns out it houses the General Theological Seminary of the Episcopal Church, on land donated by Clement C. Moore in1819. The acreage was part of the apple orchard on his estate. The oldest building dates from 1836, with other brick and stone structures also from the 19th century. Within the E-shaped Seminary is a park-like setting called the Close, a very secret garden.The buildings encompass a full city block, from 20th to 21st St and from 10th to 9th Aves. and you can peer though the wrought iron fencing to see just a bit. The only entrance to the garden for visitors is on 21st. st near 10th. Though the brochure says visitors are welcome, you must buzz at the gate, and gain admission by leaving some ID with the receptionist, (no charge for admission or brochure). Behind those sturdy brick walls are a library and chapel whichare also worth a visit. GardenBytes suggests you go sit under the old London Plane trees, read, breathe deeply and contemplate life. It's a totally serene spot.
The Seminary was entered on the National Register of Historic Places in 1977. As for flowers an herbs, there are some but they won't be the highlight of your visit.