Sienna favors players who have excellent reflexes and are skilled in rushing/breaching through areas. Moreover, the complex structure of the map, long passageways with scarce amounts to take cover, and the numerous spots that contain ambushes make Sienna one of the less favorable maps among Counter-Strike players. Not only the poor map design makes newcomers easily confused in fully memorizing the map, players are defenseless against enemy snipers across the wide-open map thus making escape nearly impossible.
There are a few pathways in which traversing players may not have enough time to either hide or initiate a counter-attack in the middle and side of the map as a sniper could be awaiting for victims on the other side. Due to this, it is rare for players to wander away from the bombsites, especially bombsite A, where adequate cover is available.
This is where most of the conflict is taking place in nearly every round. Bombsite A is close to the Terrorists, unlike Bombsite B, while the courtyard will often be occupied by the Counter-Terrorists. Generally, the Counter-Terrorists will have the major advantage as there is a small tower that contains a suitable sniper nest and can overlook the bombsite while the Terrorists can quietly walk around the bomb target.
Interestingly, the bomb does not have to be planted on the spot with the large red "target crosshair". It can be planted on the grass and even on the stairs, which makes eliminating the bomber harder to complete as a Counter-Terrorist.
One thing is for granted however, even if the bomb is not planted, the combat involved in Bombsite A is very intense to a great level and it is recommended to keep a distance away from enemies, unless there are only a few opponents. It is worthy to note that if there are numerous amounts of players, the cramped spaces in this area makes movement through the map harder to progress and HE grenades are frequently used by many players.
For some players, Bombsite B is just like Bombsite A only it is smaller and offers additional cover behind some crates. Combat is the least likely to occur here since the snipers in the long passageways (where the side and middle paths are located) that lead to site B may have already claimed victims. Often times, the windows offer snipers a chance to shoot and take cover thus discouraging players who want to enter Bombsite B, especially the Terrorists.
These paths are often proceeded with caution as experienced players are well aware of the ambushes and the snipers that are camping on the other side of the path. Sometimes, skilled players can throw grenades, especially flashbangs, around a corner and can finish off stunned enemies or use the chance to flee and attack from another angle. Sometimes, the M249 can be utilized to easily eliminate large clustered groups of enemies due to the narrow routes that players often abhor. Take note that smoke grenades can provide cover from snipers and can allow players to retreat or storm around the area. Due to these reasons, many players tend to only use these paths as a last resort to plant the bomb or for infiltration purposes.