diff --git a/birdvisu/visualisation/annotators.py b/birdvisu/visualisation/annotators.py
new file mode 100644
index 0000000..55e3f3f
--- /dev/null
+++ b/birdvisu/visualisation/annotators.py
@@ -0,0 +1,185 @@
+"""Annotators for visualising.
+
+Many of these should be somewhere else, because they make assumptions not
+related to visualisation. Also, only the currently needed annotators were
+written."""
+
+from enum import Enum, auto
+from dataclasses import dataclass
+import re
+import random
+from PySide6 import QtCore, QtGui, QtWidgets
+
+# Classification
+
+class DifferenceStatus:
+	"""Describes differences between two topologies"""
+	NORMAL = auto()
+	MISSING = auto()
+	EXTRA = auto()
+	DISCREPANCY = auto()
+
+def difference_annotator(at, reference_src='reference', actual_src='actual'):
+	"""Adds DifferenceStatuses according to which sources provided which part
+	of topology"""
+
+	topo = at.topology
+	for data, annot in [
+			(topo.routers, at.router_annotations),
+			(topo.networks, at.network_annotations),
+			(topo.links, at.link_annotations),
+			]:
+		for k, v in data.items():
+			verdict = DifferenceStatus.NORMAL
+			if actual_src not in v.sources:
+				verdict = DifferenceStatus.MISSING
+			if reference_src not in v.sources:
+				verdict = DifferenceStatus.EXTRA
+			# Nodes currently cannot have discrepant information (provided the
+			# Topology.is_valid())
+			if data is topo.links:
+				if k.metric < 0:
+					verdict = DifferenceStatus.DISCREPANCY
+			
+			# TODO: We should probably disallow mutating previous AnnotatedTopologies.
+			annot[k].append(verdict)
+	return at
+
+# TODO: annotator for routing trees
+
+
+
+# Layouting
+
+@dataclass
+class Position:
+	x: float
+	y: float
+
+def extract_positions(at, directive='visualisation default'):
+	topo = at.topology
+	for data, annot in [
+			(topo.routers, at.router_annotations),
+			(topo.networks, at.network_annotations),
+			]:
+		for k, v in data.items():
+			visu_directive = None
+			for details in k.all_details:
+				visu_directives = list(filter(lambda x: x[0] == directive, details))
+				if len(visu_directives) > 0:
+					visu_directive = visu_directives[-1] # Use the last one found.
+			position = None
+			if visu_directive is not None:
+				for pos in visu_directive[1]:
+					m = re.match(r'position \[([0-9.]+) ([0-9.]+)\]', pos)
+					if pos is not None:
+						x, y = m.groups()
+						position = Position(x = float(x), y = float(y))
+			if position is not None:
+				annot[k].append(position)
+	return at
+
+def random_posiiton(at):
+	# Fallback when no position could be extracted
+	# TODO: this should use some kind of heuristic or existing layout engine.
+	topo = at.topology
+	for data, annot in [
+			(topo.routers, at.router_annotations),
+			(topo.networks, at.network_annotations),
+			]:
+		for k, v in data.items():
+			if len(annot[k]) > 0 and not isinstance(annot[k][-1], Position):
+				annot[k].append(Position(
+					# This is really last resort, so expecting the canvas to be
+					# FullHD is as good assumption as any.
+					x = float(random.randint(0, 1920)),
+					y = float(random.randint(0, 1080)),
+					))
+	return at
+
+
+# Rendering
+
+def assign_brushes(at):
+	for annot in [
+			at.router_annotations,
+			at.network_annotations,
+			at.link_annotations,
+			]:
+		for tags in annot.values():
+			statuses = list(filter(lambda x: isinstance(x, DifferenceStatus), tags))
+			status = statuses[-1] if len(statuses) > 0 else DifferenceStatus.DISCREPANCY # should always have something.
+			color = {
+				DifferenceStatus.NORMAL: 'black',
+				DifferenceStatus.EXTRA: 'green',
+				DifferenceStatus.MISSING: 'red',
+				DifferenceStatus.DISCREPANCY: 'blue',
+				}[status]
+			tags.append(QtGui.QBrush(QtGui.QColor(color)))
+	return at
+
+def create_qgritems(at):
+	# qgritem = QGraphicsItem
+	# TODO: reasonable visualisation, not just squares :-)
+	# - this probably involves creatin custom qgritems
+	#   - We will need own qgritems anyway to handle interaction (e.g.
+	#   resolving to Router objects)
+	topo = at.topology
+	for rk, r in topo.routers.items():
+		size = 30
+		brush = None
+		for tag in at.router_annotations[rk][-1::-1]:
+			if isinstance(tag, QtGui.QBrush):
+				brush = tag
+				break
+		pos = None
+		for tag in at.router_annotations[rk][-1::-1]:
+			if isinstance(tag, Position):
+				pos = tag
+				break
+		x = pos.x
+		y = pos.y
+
+		shape = QtWidgets.QGraphicsRectItem(x, y, size, size)
+		shape.setBrush(brush)
+		label = QtWidgets.QGraphicsSimpleTextItem(rk, parent=shape)
+		at.router_annotations[rk].append(shape)
+
+	for nk, n in topo.networks.items():
+		size = 10
+		brush = None
+		for tag in at.network_annotations[nk][-1::-1]:
+			if isinstance(tag, QtGui.QBrush):
+				brush = tag
+				break
+		pos = None
+		for tag in at.network_annotations[nk][-1::-1]:
+			if isinstance(tag, Position):
+				pos = tag
+				break
+		x = pos.x
+		y = pos.y
+
+		shape = QtWidgets.QGraphicsRectItem(x, y, size, size)
+		shape.setBrush(brush)
+		label = QtWidgets.QGraphicsSimpleTextItem(nk, parent=shape)
+		at.network_annotations[nk].append(shape)
+
+	for lk, l in topo.links.items():
+		rid = l.router.ident
+		nid = l.network.ident
+
+		rpos = None
+		for tag in at.router_annotations[rid][-1::-1]:
+			if isinstance(tag, Position):
+				rpos = tag
+				break
+		npos = None
+		for tag in at.network_annotations[nid][-1::-1]:
+			if isinstance(tag, Position):
+				npos = tag
+				break
+
+		line = QtWidgets.QGraphicsLineItem(rpos.x, rpos.y, npos.x, npos.y)
+		at.link_annotations[lk].append(line)
+