The mosque is more similar in type to a mausoleum
than a four-iwan mosque. Architectural historians ascribe this either to the
fact that members of the Shah’s family had used it for private worship or that
it had functioned as a women’s sanctuary. 

The portal iwan is not aligned with the maydan’s elevation,
but is preceded by a recessed small court which flows from the maydan and is
linked, on its north and south sides, to the continuous corridor that envelopes
the maydan’s mercantile facilities. The main entrance to the mosque is located
on the east side of this small court. The structure itself is not aligned
perpendicularly to the maydan’s eastern wall, but lies at an angle (almost 45
degrees) against the maydan’s wall. As a result, when viewed from the maydan,
the mosque’s main portal iwan and dome do not fall on the same axis, as is
always the case in other mosques, but instead the dome appears behind the main
portal iwan as if having slid 6.5 meters to the right from its axis. This
asymmetrical layout was initially introduced to reconcile the (southwest)
direction of Mecca with the placement of the mihrab on the qibla wall, and adds
visual complexity to the structure. 

Contrary to the maydan’s sand-colored brick elevation, the
portal iwan is elaborately ornamented in colorful mosaics. It is built as a
recessed area on the eastern wall of the court, an elevated platform raised by
four steps from the court level. An inscription band in white on a dark blue
background runs horizontally on the three sides of the portal niche, above
which begins the iwan’s vault, comprising four clusters of muqarnases made of
small glazed-tiles units. These four clusters ascend to inscribe a concentric
floral medallion. The pointed-arch doorway is located below the inscription
band and is flanked by two panels of mosaics of floral arabesques with motifs
in yellow, white, and blue on a dark blue background. These panels rest on top
of a continuous marble dado. 

The offset entry does not allow the visitor to enter the
prayer chamber directly from the maydan by passing through the main portal
iwan, which is aligned on the east-west axis. Due to the mosque’s alignment on
the northeast-southwest axis, upon entering the mosque one walks along two
corridors, oriented respectively to the northeast and southeast, which are
placed adjacent to the northwest and northeast walls of the prayer chamber.
Turning southwest to face the qibla wall, one enters the domed chamber to see
the mihrab on the opposite wall. This journey into gradual deepening into
darkness and reemergence into a room bathed with light reflected on the glazed
revetment is one of the most rewarding experiences of the building. 

In contrast to the grand size of the maydan’s space, the
Shaykh Lutfallah mosque is very small and is comprised of a single domed
chamber (19 meters on a side), surrounded by rooms (which possibly functioned
as service areas) on its sides, and preceded by a portal iwan overlooking the
maydan. The two rooms accessed from the corridor which envelopes the sanctuary
dome measure 6 by 9 meters; one is found on the western side of the corridor,
and the other along the far end of the eastern wall. A third room (8 by 16
meters) is located on the exterior of the southern wall of the sanctuary, and
is accessed via the corridor running along the maydan wall and then turning
right after the vestibule area. Although the Shaykh Lutfallah is not one
rectangular structure, its masses can be measured as one rectangular area of 44
by 30 meters and an additional rectangular service area comprising
approximately 152 square meters. 

The dome is one of the few single-shell domes of the Safavid
architecture with a structure consisting of three levels. Four squinches of
pointed-arched panels, framed by an inscription band in white and blue
demarcated by light blue cable moldings, ascend from the floor and support a
sixteen kite-shaped shields that, in turn, support the drum, which comprises
sixteen arched panels. The drum is ornamented with alternating double-grilles
windows with an arabesque pattern. The interior dome has a sunburst from which
descend medallions inscribing floral motifs, which become larger as they
descend away from the center. The exterior of the dome is ornamented with an
arabesque of a floral motif in white, blue, and black against a yellow
background 

The Shaykh Lutfallah mosque is viewed by historians and
visitors as one of the most important architectural projects built on Isfahan’s
maydan, prominent for its location, scale, design, and ornament. 

Reference: 

https://archnet.org/sites/1623