Attached to the north-eastern corner of the Pœcile is a fine building, in the form of a recess, with a semicircular niche turned towards the north, which, from the connection of the Stoic philosophy with the Stoa Pœcile at Athens, has been called the Temple or School of the Stoics. It was possibly a hall for conversation and discussion. [Sidenote: Library.] Opening from this school, towards the north-east, is a building in the form of two concentric circles. Between the two circular parts there was a canal filled with water. This edifice was probably a swimming-bath. It appears to have been very highly ornamented with precious marbles and sculptures, most of which were taken to Rome by Cardinal Alessandro Farnese, and others to Tivoli by Cardinal Ippolito d’Este. The ruin commonly goes by the name of Theatrum Maritimum. A little farther to the north-east is a quadrilateral court, 200 feet wide, which was surrounded by a portico with Corinthian columns. On the north-west side of this court are the buildings usually supposed to belong to the library, and called the Greek and Latin libraries. They consist of a large number of rooms, more or less preserved, which may have been ante-rooms and chambers for the attendants and librarians. In the centre of the north-western side of the court is a well-preserved Nymphæum, and on the north-east a long corridor with windows towards the south, which may be called a Helio Caminus, or room for basking in the sun, from its resemblance to the place so called by Pliny at his Laurentine villa. The ruins to the north-east of these, towards the Valley of Tempe, are thought by Nibby to be the remains of a suite of rooms belonging to one wing of the imperial palace, but their plan is very imperfectly known. [Sidenote: Palace.] The great mass of the imperial apartments were farther to the south-east, and were grouped round three large courts of dazzling magnificence. The most splendid of those, which afforded spoil for generations of plunderers, is called by Piranesi, from the richness of its decorative work, the Piazza d’Oro. Round the courts were numberless suites of rooms and several large recesses, a basilica, and a great hall now called Eco Corintio, formerly supported on vast granite columns, and cased with slabs of the choicest marbles. [Sidenote: Stadium.] The Stadium lies in a direction at right-angles to the southern side of the Pœcile. The curved end is towards the south. Between the swimming-bath and the northern, or square end of the Stadium, are some bath-rooms for the use of the athletes, and on the west side stands a temple surrounded by a sacred enclosure formed by two vast semicircular walls ornamented with niches. On the eastern side are more rooms, and a magnificent quadrilateral covered way. [Sidenote: Thermæ.]