Observation Towers differ from most architecture. In general architecture presents an exterior image and holds an interior function. Observation towers may have an exterior image, but they lack an interior function. Their function is also exterior. that of viewing the landscape around them. This gives a great freedom for design, there are no bathrooms to fit in, no doors to place, only a stair and a platform. The view is what is important. Views both out from the tower and views of the tower itself. The observation tower not only creates vistas, but also is a point of reference within other vistas.
While observations do not have an interior program, they do have an overall program. These can be broken down into 3 basic categories. The first is for observation. This is what we are looking at here and all the other programs incorporate this as well. The second type is military. These are probably the first type of observation tower to be built. They provide protection and can also be used to demarcate a border. The final programmatic type is the symbolic tower. These are usually found in urban settings and may have initially had a military purpose. They convey a message beyond their view, one of status and again marking of a location. The tower is meant to be seen from a distance, proclaiming a symbolic importance to the area in which it is found. Simultaneously, from the observation platform, the area to which the tower gives its symbolic importance can be seen.
There are in infinite variety of towers, but most of these fall into a few simple formal categories. These are usually binary pairs of choices, open/closed, attach/attached detached, etc. It is worth taking a closer look to at these possibilities, to see what each has to offer.
The closed tower is often associated with the military or symbolic programmatic typologies as the solid form works better as a defensive structure or as a visible marker from the distance. The closed tower can offer specific views as the users does not have continuous access to the exterior spaces of an open tower.
Closed towers are not necessarily massive structures. By controlling the proportions between the platform and the tower it can appear slender. By creating screens a tower can hover between open and closed. Or by using only certain closed sides the views can be focus on desired elements.
Open towers are more appropriate for the function of observation towers for several reasons. They do not need to be a solid defence or an imposing symbol as their function is to provide a view and not create a marker. They are also lighter structurally, thus cheaper and easier to maintain. While these may seem as mundane arguments, the often remote or secluded location of such towers gives added importance to such considerations.
By being open these types of towers allow for views through them as well as from them. They blend better into their natural settings, and create less of an impact on their surroundings.
Open designs can also take advantage of the structure to create interesting forms.
The stair of the observation tower is an important aspect of the design. The stair is the most dynamic element of the tower, connecting the base to the viewing platform, and can be used to manipulate the viewing experience.
Using the stair as an exterior element adds to its importance and prominence.
As an exterior element, the stair can become a dominant architectural feature, giving the body of the tower articulation and balancing it with the typically dominant element of the viewing platform. It can also work to manipulate the relationship between solid and void.
The exterior stair can also be pulled away from the tower to create a different type of approach, allowing the horizontal path leading to the tower blend into the vertical element of the stair more smoothly.
By placing the stair inside the structure of the tower, the design becomes more unitary. It also allows for the possibility of integrating the stair with the structure, to create a hybrid system where the stair works as the cross bracing that stabilizes the legs of the tower.
The interior stair moves to the background and allows for the elements of the platform and structure to become the active architectural features. Using the landings from the stairs is one way to create extra viewing platforms. The structure can also be freed from the stairs, creating a formal statement.
Because the stair is an element of circulation, it can move between being exterior and interior. Hybrids of these typologies can use the advantages of each to create a more dynamic structure.
Using a single platform gives preference to single view of the landscape from a certain height. Based on what and how the platform is placed, certain aspects of the surroundings will be favored over others. A low platform can be used to just create a physical break from the ground, or just help for bird watching. A taller tower will give a wider and farther view, and is necessary if their are trees or buildings in the immediate area.
The single platform does not have to be a static element at the top of the tower. By manipulating the plan and creating a directionality to the platform certain views are preferenced to others. And it can be used along with other elements, such as the stairs and roof to create an architectural composition that is as complex as a multiple platform structure.
Multiple platforms offer a greater range of possibilities in offering different views and creating a dynamic circulation through the tower. By having multiple stopping points it activates the body of the tower.
Multiple Platforms can be set at different heights to create an upward progression of vantage points which steadily increase the view. Or they can create a hierarchy of different levels, with one dominant view and secondary views which may be oriented toward specific details. They can also be used to break the vertical axis of the tower, creating an almost unstable feeling.
Towers can also be part of a building. This can work in many ways, but also has to be done with care, as the proportions of each element must be taken into consideration. By combining the two elements different paths can be taken, using the upper floors of a building to gain direct access to the tower at an already raised level. This also returns the tower to the function of a marker for the building in the landscape.
There are several ways to attach the tower to a building. Or it is possible to use the building itself as a tower. These approaches can be used for specific situations where the architecture calls for a different solution.
Structure is the most important element of the viewing tower. Not only does it hold high the viewing platform, but also creates much of the formal aspect of the tower. Typically standing on four legs with cross bracing going up for stability, this typology leaves a lot of room for experimentation and design.
The base of the tower is set in concrete foundations. Each post sits on its own buried sunken foundation, though a large pad can also be used. Cable stays can also be used to stabilize a thinner structure.
The main body of the tower is composed of vertical legs which are cross braced. This creates what amounts to a vertical truss. The typical materials for this type of tower are wood with metal joints and reinforcements. It is a simple structure, but has infinite variations and can be modified to suit interior or exterior stairs as well as multiple platforms. Wood is a plastic material and can be manipulated to create complex structures.
STAIR & PLATFORM
The stairs and platform of the tower can work in many ways as relates to the structure of the tower. They can be independant pieces which hang off of and sit on the body of the tower. Or they can be active parts of the structure, helping to stabilize and support one another. These elements are opportunities for both formal and structural experimentation.
This tower by Japanese architect Shiguru Ban is made out of cardboard tubes with metal connectors. Here he uses a diagonal grid and conic shape to create a simple elegant structure. This is an example of an alternative structural system that can be used for this type of construction. While cardboard is a unusual material and may not be well suited for all situations, it illustrates the strength that the diagonal grid gives the structure.
It is interesting to look at some contemporary examples of tower structures to get a fell for the possibilities that new approaches and materials can suggest.
This Teahouse by Terunobu Fugimori is a playful example, but differs from the observation tower in the key point made at he start. The tea house is an intensely internal program, while the observation tower is a purely external function. But it does bring up another interesting point that is related to the observation tower. Fugimori loft his teahouse off the ground to create a detachment and isolation. This also happens in the observation tower.
This birdwatching tower is an interesting because it is mostly solid, yet seems to almost melt into the landscape. It also is a good example of how to create a directional view. Not only is the tower open to the desired direction, but the entrance sequence also follows this axis.
Another example of the diagonal grid structure. This one is interesting in that the model is being woven together, though the finished structure does not seem to keep this aspect of the design. Also interesting in how the structure wraps around the entire tower, including the viewing platforms.
ANDERSON ANDERSON ARCHITECTS
The experimental tower design shows the possibility of using translucent materials to create a different type of atmosphere. It also is an example of a single mast structure that is held up with cable stays.
Another typology for the tower. This one departs from the typical image of the tower with a platform on top. Here a series of boxes are stacked on top of each other, each with its own platform and different view. It is also interesting how the design incorporates additional functions onto its sides.
GMP ARCHITECTS / THE EVOLVER
These two examples incorporate many different possibilities. Both use wooden structural systems; on the left is something that could be read as a cross between the diagonal grid and a variation on the traditional tower bracing, while in the right a more plastic approach of a circular ribbed structure is used. In both the path is controlled to direct the view to a specific direction. It is also interesting to see the play of the reflection of these towers in the water, another element which could be considered.
Finally these birdcages are meant to provoke. One could imagine a observation tower where the people are being watched or just a play between the birdwatcher being trapped in a birdcage. These are meant to point into different and unknown directions where the design comes from a source outside tower design yet can create a relationship with it through form, program, material, or metaphor.