One of the possible solutions to the task in https://neil.fraser.name/news/2013/03/16/

maze.py

# coding: utf-8
import copy

maze = []

# Read the maze into an array
with open('maze1.txt') as f:
    for line in f.readlines():
        maze.append([int(i) for i in line.strip()])

# A list of seen points
seen = copy.deepcopy(maze)

MAZE_HEIGHT = len(maze)
MAZE_LENGTH = len(maze[0])


def all_points(array):
    for x, row in enumerate(array):
        for y, point in enumerate(row):
            yield x, y


def get_entry_point():
    """ Searches a first unseen point in the maze """
    for x, y in all_points(maze):
        if not seen[x][y]:
            return x, y
    return None

# Obtain a list of linked components
components = []
entry_point = get_entry_point()
while entry_point:
    component = [entry_point]
    queue = [entry_point]
    while len(queue):
        x, y = queue.pop()
        seen[x][y] = 1
        possible_neighbors = [(x, y - 1), (x, y + 1), (x - 1, y), (x + 1, y)]
        # Exclude all neighbors with coordinates out of range
        neighbors = [(x, y) for x, y in possible_neighbors if 0 <= x < MAZE_HEIGHT and 0 <= y < MAZE_LENGTH]
        for point in neighbors:
            x, y = point
            if point not in component and maze[x][y] == 0:
                component.append(point)
                queue.append(point)
    components.append(component)
    entry_point = get_entry_point()


def does_not_contact_perimeter(area):
    """ Checks if an area touches the borders if the maze """
    for x, y in area:
        if x == 0 or y == 0 or x == MAZE_HEIGHT - 1 or y == MAZE_LENGTH - 1:
            return False
    return True

# Exclude all areas that contact the perimeter
# and get the list of enclosed areas accordingly
enclosed_areas = list(filter(does_not_contact_perimeter, components))

print("The amount of enclosed areas: %d" % len(enclosed_areas))

# Figure out the area of the largest one
if len(enclosed_areas):
    largest_area = max(enclosed_areas, key=lambda area: len(area))

    # Find the key points of the area
    def is_point_key(point):
        x, y = point
        return (x - 2) % 4 == 0 and y % 4 == 0

    key_points = list(filter(is_point_key, largest_area))
    print("The area of the largest one: %d" % len(key_points))