Secret locations

The Secret Locations are memories which must be completed through a combination of free-running and puzzle solving. Many of these locations were scattered throughout Italy and Consiantinople, and were explored by the Assassin Ezio Auditore da Firenze during the Renaissance. In gameplay terms, most of these were optional, with the exception of the Assassin's Tomb inside the Santa Maria Novella, the Lair of Romulus inside the Terme di Traiano, and the four locations traversed in order to collect the Seals of Altaïr.

Assassin Tombs
The Assassin Tombs were seven landmarks around Italy, each containing the tomb of an Assassin, each of whom were said to have protected the freedom of mankind when it was most threatened. Each tomb also contained (with the exception of Domenico Auditore's tomb in the Auditore Crypt) an Assassin seal, which were used to obtain the Armor of Altaïr in the Sanctuary.


 * Santa Maria Novella - contained the tomb of Darius
 * Il Duomo - contained the tomb of Iltani
 * Auditore Family Crypt - contained the tomb of Domenico Auditore
 * Torre Grossa - contained the tomb of Wei Yu
 * Rocca di Ravaldino - contained the tomb of Qulan Gal
 * Basilica di San Marco - contained the tomb of Amunet
 * Santa Maria della Visitazione - contained the tomb of Leonius

Templar Lairs
The Templar Lairs (with the exception of the Palazzo Medici) hide treasure that presumably belonged to and funded the activities of the Templar Order. All of these can be accessed through a wooden door, marked with a large red cross.
 * Palazzo Medici in Florence
 * Santa Maria Dei Frari in Venice
 * Arsenal Shipyard in Venice

Rome
Secret locations were also found in Rome, in the form of Lairs of Romulus. There were six of them, spread throughout the vast city. Additionally, there are two Templar Lairs, which were also found in Rome

Completing all of the Lairs of the Followers of Romulus would allow Ezio to obtain two of the treasures they guarded, the Armor of Brutus and the Dagger of Brutus. Through traversing these locations, Ezio also obtained some special documents that gave background details on the cult.

Lairs of Romulus

 * Catacombe di Roma
 * Terme di Traiano
 * Il Colosseo
 * Cloaca Maxima
 * Palazzo Laterano
 * Basilica di San Pietro

Templar Lairs

 * Aqueducts
 * Trajan Market

Constantinople
In Constantinople, there were many secret locations that could be explored.

Locations of Seals of Altaïr

 * The Yerebatan Cistern


 * Galata Tower


 * The Forum of the Ox


 * The Maiden's Tower

Others

 * Hagia Sophia
 * Vlad the Impaler's Prison

Trivia

 * In the tomb hidden in Santa Maria della Visitazione, if you activate the lever, stand on the edge of the floor and stare into the water, you'll see a large figure move through the water after a minute, swimming past while staring at you with what appears to be a yellow eye. After the lever's time limit runs out, when you re-activate it and stand on the same spot and wait, a giant tentacle will shoot out of the water, though Ezio dodges before it manages to hit him.
 * Solomon's Temple in Assassin's Creed is considered to be similar to a secret location; or more precisely, a Templar Lair, due to its linear mission and underground setting.
 * In the tomb in the Basilica di San Marco, the banners clearly show the poison symbol, despite the Seal bearing the snake symbol.